## File: README.md

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- [Design goals](#design-goals)
- [Sponsors](#sponsors)
- [Support](#support) ([documentation](https://json.nlohmann.me), [FAQ](https://json.nlohmann.me/home/faq/), [discussions](https://github.com/nlohmann/json/discussions), [API](https://json.nlohmann.me/api/basic_json/), [bug issues](https://github.com/nlohmann/json/issues))
- [Quick reference](#quick-reference)
- [Examples](#examples)
  - [Read JSON from a file](#read-json-from-a-file)
  - [Creating `json` objects from JSON literals](#creating-json-objects-from-json-literals)
  - [JSON as a first-class data type](#json-as-a-first-class-data-type)
  - [Serialization / Deserialization](#serialization--deserialization)
  - [STL-like access](#stl-like-access)
  - [Conversion from STL containers](#conversion-from-stl-containers)
  - [JSON Pointer and JSON Patch](#json-pointer-and-json-patch)
  - [JSON Merge Patch](#json-merge-patch)
  - [Implicit conversions](#implicit-conversions)
  - [Conversions to/from arbitrary types](#arbitrary-types-conversions)
  - [Specializing enum conversion](#specializing-enum-conversion)
  - [Binary formats (BSON, CBOR, MessagePack, UBJSON, and BJData)](#binary-formats-bson-cbor-messagepack-ubjson-and-bjdata)
- [Customers](#customers)
- [Ecosystem](#ecosystem)
- [Supported compilers](#supported-compilers)
- [Integration](#integration)
  - [CMake](#cmake)
  - [Package Managers](#package-managers)
  - [Pkg-config](#pkg-config)
- [License](#license)
- [Contact](#contact)
- [Thanks](#thanks)
- [Used third-party tools](#used-third-party-tools)
- [Notes](#notes)
- [Execute unit tests](#execute-unit-tests)

## Design goals

There are myriads of [JSON](https://json.org) libraries out there, and each may even have its reason to exist. Our class had these design goals:

- **Intuitive syntax**. In languages such as Python, JSON feels like a first-class data type. We used all the operator magic of modern C++ to achieve the same feeling in your code. Check out the [examples below](#examples) and you'll know what I mean.

- **Trivial integration**. Our whole code consists of a single header file [`json.hpp`](https://github.com/nlohmann/json/blob/develop/single_include/nlohmann/json.hpp). That's it. No library, no subproject, no dependencies, no complex build system. The class is written in vanilla C++11. All in all, everything should require no adjustment of your compiler flags or project settings. The library is also included in all popular [package managers](https://json.nlohmann.me/integration/package_managers/).

- **Serious testing**. Our code is heavily [unit-tested](https://github.com/nlohmann/json/tree/develop/tests/src) and covers [100%](https://coveralls.io/r/nlohmann/json) of the code, including all exceptional behavior. Furthermore, we checked with [Valgrind](https://valgrind.org) and the [Clang Sanitizers](https://clang.llvm.org/docs/index.html) that there are no memory leaks. [Google OSS-Fuzz](https://github.com/google/oss-fuzz/tree/master/projects/json) additionally runs fuzz tests against all parsers 24/7, effectively executing billions of tests so far. To maintain high quality, the project is following the [Core Infrastructure Initiative (CII) best practices](https://bestpractices.coreinfrastructure.org/projects/289). See the [quality assurance](https://json.nlohmann.me/community/quality_assurance) overview documentation.

Other aspects were not so important to us:

- **Memory efficiency**. Each JSON object has an overhead of one pointer (the maximal size of a union) and one enumeration element (1 byte). The default generalization uses the following C++ data types: `std::string` for strings, `int64_t`, `uint64_t` or `double` for numbers, `std::map` for objects, `std::vector` for arrays, and `bool` for Booleans. However, you can template the generalized class `basic_json` to your needs.

- **Speed**. There are certainly [faster JSON libraries](https://github.com/miloyip/nativejson-benchmark#parsing-time) out there. However, if your goal is to speed up your development by adding JSON support with a single header, then this library is the way to go. If you know how to use a `std::vector` or `std::map`, you are already set.

See the [contribution guidelines](https://github.com/nlohmann/json/blob/develop/.github/CONTRIBUTING.md#please-dont) for more information.

## Sponsors

You can sponsor this library at [GitHub Sponsors](https://github.com/sponsors/nlohmann).

### :raising_hand: Priority Sponsor

- [Martti Laine](https://github.com/codeclown)
- [Paul Harrington](https://github.com/phrrngtn)
- [Mercedes-Benz Group](https://github.com/mercedes-benz)
- [Ryan McCaffery](https://github.com/mccaffers)

### :label: Named Sponsors

- [Michael Hartmann](https://github.com/reFX-Mike)
- [Stefan Hagen](https://github.com/sthagen)
- [Steve Sperandeo](https://github.com/homer6)
- [Robert Jefe Lindstädt](https://github.com/eljefedelrodeodeljefe)
- [Steve Wagner](https://github.com/ciroque)

### Further support

The development of the library is further supported by JetBrains by providing free access to their IDE tools.

[](https://jb.gg/OpenSourceSupport)

Thanks everyone!

## Support

:question: If you have a **question**, please check if it is already answered in the [**FAQ**](https://json.nlohmann.me/home/faq/) or the [**Q&A**](https://github.com/nlohmann/json/discussions/categories/q-a) section. If not, please [**ask a new question**](https://github.com/nlohmann/json/discussions/new) there.

:books: If you want to **learn more** about how to use the library, check out the rest of the [**README**](#examples), have a look at [**code examples**](https://github.com/nlohmann/json/tree/develop/docs/mkdocs/docs/examples), or browse through the [**help pages**](https://json.nlohmann.me).

:construction: If you want to understand the **API** better, check out the [**API Reference**](https://json.nlohmann.me/api/basic_json/) or have a look at the [quick reference](#quick-reference) below.

:bug: If you found a **bug**, please check the [**FAQ**](https://json.nlohmann.me/home/faq/) if it is a known issue or the result of a design decision. Please also have a look at the [**issue list**](https://github.com/nlohmann/json/issues) before you [**create a new issue**](https://github.com/nlohmann/json/issues/new/choose). Please provide as much information as possible to help us understand and reproduce your issue.

There is also a [**docset**](https://github.com/Kapeli/Dash-User-Contributions/tree/master/docsets/JSON_for_Modern_C%2B%2B) for the documentation browsers [Dash](https://kapeli.com/dash), [Velocity](https://velocity.silverlakesoftware.com), and [Zeal](https://zealdocs.org) that contains the full [documentation](https://json.nlohmann.me) as an offline resource.

## Quick reference

- **Constructors** [basic_json](https://json.nlohmann.me/api/basic_json/basic_json), [array](https://json.nlohmann.me/api/basic_json/array), [binary](https://json.nlohmann.me/api/basic_json/binary), [object](https://json.nlohmann.me/api/basic_json/object)
- **Object inspection**: [type](https://json.nlohmann.me/api/basic_json/type), [operator value_t](https://json.nlohmann.me/api/basic_json/operator_value_t), [type_name](https://json.nlohmann.me/api/basic_json/type_name), [is_primitive](https://json.nlohmann.me/api/basic_json/is_primitive), [is_structured](https://json.nlohmann.me/api/basic_json/is_structured), [is_null](https://json.nlohmann.me/api/basic_json/is_null), [is_boolean](https://json.nlohmann.me/api/basic_json/is_boolean), [is_number](https://json.nlohmann.me/api/basic_json/is_number), [is_number_integer](https://json.nlohmann.me/api/basic_json/is_number_integer), [is_number_unsigned](https://json.nlohmann.me/api/basic_json/is_number_unsigned), [is_number_float](https://json.nlohmann.me/api/basic_json/is_number_float), [is_object](https://json.nlohmann.me/api/basic_json/is_object), [is_array](https://json.nlohmann.me/api/basic_json/is_array), [is_string](https://json.nlohmann.me/api/basic_json/is_string), [is_binary](https://json.nlohmann.me/api/basic_json/is_binary), [is_discarded](https://json.nlohmann.me/api/basic_json/is_discarded)
- **Value access**; [get](https://json.nlohmann.me/api/basic_json/get), [get_to](https://json.nlohmann.me/api/basic_json/get_to), [get_ptr](https://json.nlohmann.me/api/basic_json/get_ptr), [get_ref](https://json.nlohmann.me/api/basic_json/get_ref), [operator ValueType](https://json.nlohmann.me/api/basic_json/operator_ValueType), [get_binary](https://json.nlohmann.me/api/basic_json/get_binary)
- **Element access**: [at](https://json.nlohmann.me/api/basic_json/at), [operator[]](https://json.nlohmann.me/api/basic_json/operator[]), [value](https://json.nlohmann.me/api/basic_json/value), [front](https://json.nlohmann.me/api/basic_json/front), [back](https://json.nlohmann.me/api/basic_json/back)
- **Lookup**: [find](https://json.nlohmann.me/api/basic_json/find), [count](https://json.nlohmann.me/api/basic_json/count), [contains](https://json.nlohmann.me/api/basic_json/contains)
- **Iterators**: [begin](https://json.nlohmann.me/api/basic_json/begin), [cbegin](https://json.nlohmann.me/api/basic_json/cbegin), [end](https://json.nlohmann.me/api/basic_json/end), [cend](https://json.nlohmann.me/api/basic_json/cend), [rbegin](https://json.nlohmann.me/api/basic_json/rbegin), [rend](https://json.nlohmann.me/api/basic_json/rend), [crbegin](https://json.nlohmann.me/api/basic_json/crbegin), [crend](https://json.nlohmann.me/api/basic_json/crend), [items](https://json.nlohmann.me/api/basic_json/items)
- **Capacity**: [empty](https://json.nlohmann.me/api/basic_json/empty), [size](https://json.nlohmann.me/api/basic_json/size), [max_size](https://json.nlohmann.me/api/basic_json/max_size)
- **Modifiers**: [clear](https://json.nlohmann.me/api/basic_json/clear), [push_back](https://json.nlohmann.me/api/basic_json/push_back), [operator+=](https://json.nlohmann.me/api/basic_json/operator+=), [emplace_back](https://json.nlohmann.me/api/basic_json/emplace_back), [emplace](https://json.nlohmann.me/api/basic_json/emplace), [erase](https://json.nlohmann.me/api/basic_json/erase), [insert](https://json.nlohmann.me/api/basic_json/insert), [update](https://json.nlohmann.me/api/basic_json/update), [swap](https://json.nlohmann.me/api/basic_json/swap)
- **Lexicographical comparison operators**: [operator==](https://json.nlohmann.me/api/basic_json/operator_eq), [operator!=](https://json.nlohmann.me/api/basic_json/operator_ne), [operator<](https://json.nlohmann.me/api/basic_json/operator_lt), [operator>](https://json.nlohmann.me/api/basic_json/operator_gt), [operator<=](https://json.nlohmann.me/api/basic_json/operator_le), [operator>=](https://json.nlohmann.me/api/basic_json/operator_ge), [operator<=>](https://json.nlohmann.me/api/basic_json/operator_spaceship)
- **Serialization / Dumping**: [dump](https://json.nlohmann.me/api/basic_json/dump)
- **Deserialization / Parsing**: [parse](https://json.nlohmann.me/api/basic_json/parse), [accept](https://json.nlohmann.me/api/basic_json/accept), [sax_parse](https://json.nlohmann.me/api/basic_json/sax_parse)
- **JSON Pointer functions**: [flatten](https://json.nlohmann.me/api/basic_json/flatten), [unflatten](https://json.nlohmann.me/api/basic_json/unflatten)
- **JSON Patch functions**: [patch](https://json.nlohmann.me/api/basic_json/patch), [patch_inplace](https://json.nlohmann.me/api/basic_json/patch_inplace), [diff](https://json.nlohmann.me/api/basic_json/diff), [merge_patch](https://json.nlohmann.me/api/basic_json/merge_patch)
- **Static functions**: [meta](https://json.nlohmann.me/api/basic_json/meta), [get_allocator](https://json.nlohmann.me/api/basic_json/get_allocator)
- **Binary formats**: [from_bjdata](https://json.nlohmann.me/api/basic_json/from_bjdata), [from_bson](https://json.nlohmann.me/api/basic_json/from_bson), [from_cbor](https://json.nlohmann.me/api/basic_json/from_cbor), [from_msgpack](https://json.nlohmann.me/api/basic_json/from_msgpack), [from_ubjson](https://json.nlohmann.me/api/basic_json/from_ubjson), [to_bjdata](https://json.nlohmann.me/api/basic_json/to_bjdata), [to_bson](https://json.nlohmann.me/api/basic_json/to_bson), [to_cbor](https://json.nlohmann.me/api/basic_json/to_cbor), [to_msgpack](https://json.nlohmann.me/api/basic_json/to_msgpack), [to_ubjson](https://json.nlohmann.me/api/basic_json/to_ubjson)
- **Non-member functions**: [operator<<](https://json.nlohmann.me/api/operator_ltlt/), [operator>>](https://json.nlohmann.me/api/operator_gtgt/), [to_string](https://json.nlohmann.me/api/basic_json/to_string)
- **Literals**: [operator""_json](https://json.nlohmann.me/api/operator_literal_json)
- **Helper classes**: [std::hash&lt;basic_json&gt;](https://json.nlohmann.me/api/basic_json/std_hash), [std::swap&lt;basic_json&gt;](https://json.nlohmann.me/api/basic_json/std_swap)

[**Full API documentation**](https://json.nlohmann.me/api/basic_json/)

## Examples

Here are some examples to give you an idea how to use the class.

Besides the examples below, you may want to:

→ Check the [documentation](https://json.nlohmann.me/)\
→ Browse the [standalone example files](https://github.com/nlohmann/json/tree/develop/docs/mkdocs/docs/examples)\
→ Read the full [API Documentation](https://json.nlohmann.me/api/basic_json/) with self-contained examples for every function

### Read JSON from a file

The `json` class provides an API for manipulating a JSON value. To create a `json` object by reading a JSON file:

```cpp
#include <fstream>
#include <nlohmann/json.hpp>
using json = nlohmann::json;

// ...

std::ifstream f("example.json");
json data = json::parse(f);
```

If using modules (enabled with `NLOHMANN_JSON_BUILD_MODULES`), this example becomes:
```cpp
import std;
import nlohmann.json;

using json = nlohmann::json;

// ...

std::ifstream f("example.json");
json data = json::parse(f);
```

### Creating `json` objects from JSON literals

Assume you want to hard-code this literal JSON value as a `json` object:

```json
{
  "pi": 3.141,
  "happy": true
}
```

There are various options:

```cpp
// Using (raw) string literals and json::parse
json ex1 = json::parse(R"(
  {
    "pi": 3.141,
    "happy": true
  }
)");

// Using user-defined (raw) string literals
using namespace nlohmann::literals;
json ex2 = R"(
  {
    "pi": 3.141,
    "happy": true
  }
)"_json;

// Using initializer lists
json ex3 = {
  {"happy", true},
  {"pi", 3.141},
};
```

### JSON as a first-class data type

Here are some examples to give you an idea how to use the class.

Assume you want to create the JSON object

```json
{
  "pi": 3.141,
  "happy": true,
  "name": "Niels",
  "nothing": null,
  "answer": {
    "everything": 42
  },
  "list": [1, 0, 2],
  "object": {
    "currency": "USD",
    "value": 42.99
  }
}
```

With this library, you could write:

```cpp
// create an empty structure (null)
json j;

// add a number stored as double (note the implicit conversion of j to an object)
j["pi"] = 3.141;

// add a Boolean stored as bool
j["happy"] = true;

// add a string stored as std::string
j["name"] = "Niels";

// add another null object by passing nullptr
j["nothing"] = nullptr;

// add an object inside the object
j["answer"]["everything"] = 42;

// add an array stored as std::vector (using an initializer list)
j["list"] = { 1, 0, 2 };

// add another object (using an initializer list of pairs)
j["object"] = { {"currency", "USD"}, {"value", 42.99} };

// instead, you could also write (which looks very similar to the JSON above)
json j2 = {
  {"pi", 3.141},
  {"happy", true},
  {"name", "Niels"},
  {"nothing", nullptr},
  {"answer", {
    {"everything", 42}
  }},
  {"list", {1, 0, 2}},
  {"object", {
    {"currency", "USD"},
    {"value", 42.99}
  }}
};
```

Note that in all these cases, you never need to "tell" the compiler which JSON value type you want to use. If you want to be explicit or express some edge cases, the functions [`json::array()`](https://json.nlohmann.me/api/basic_json/array/) and [`json::object()`](https://json.nlohmann.me/api/basic_json/object/) will help:

```cpp
// a way to express the empty array []
json empty_array_explicit = json::array();

// ways to express the empty object {}
json empty_object_implicit = json({});
json empty_object_explicit = json::object();

// a way to express an _array_ of key/value pairs [["currency", "USD"], ["value", 42.99]]
json array_not_object = json::array({ {"currency", "USD"}, {"value", 42.99} });
```

### Serialization / Deserialization

#### To/from strings

You can create a JSON value (deserialization) by appending `_json` to a string literal:

```cpp
// create object from string literal
json j = "{ \"happy\": true, \"pi\": 3.141 }"_json;

// or even nicer with a raw string literal
auto j2 = R"(
  {
    "happy": true,
    "pi": 3.141
  }
)"_json;
```

Note that without appending the `_json` suffix, the passed string literal is not parsed, but just used as JSON string
value. That is, `json j = "{ \"happy\": true, \"pi\": 3.141 }"` would just store the string
`"{ "happy": true, "pi": 3.141 }"` rather than parsing the actual object.

The string literal should be brought into scope with `using namespace nlohmann::literals;`
(see [`json::parse()`](https://json.nlohmann.me/api/operator_literal_json/)).

The above example can also be expressed explicitly using [`json::parse()`](https://json.nlohmann.me/api/basic_json/parse/):

```cpp
// parse explicitly
auto j3 = json::parse(R"({"happy": true, "pi": 3.141})");
```

You can also get a string representation of a JSON value (serialize):

```cpp
// explicit conversion to string
std::string s = j.dump();    // {"happy":true,"pi":3.141}

// serialization with pretty printing
// pass in the amount of spaces to indent
std::cout << j.dump(4) << std::endl;
// {
//     "happy": true,
//     "pi": 3.141
// }
```

Note the difference between serialization and assignment:

```cpp
// store a string in a JSON value
json j_string = "this is a string";

// retrieve the string value
auto cpp_string = j_string.get<std::string>();
// retrieve the string value (alternative when a variable already exists)
std::string cpp_string2;
j_string.get_to(cpp_string2);

// retrieve the serialized value (explicit JSON serialization)
std::string serialized_string = j_string.dump();

// output of original string
std::cout << cpp_string << " == " << cpp_string2 << " == " << j_string.get<std::string>() << '\n';
// output of serialized value
std::cout << j_string << " == " << serialized_string << std::endl;
```

[`.dump()`](https://json.nlohmann.me/api/basic_json/dump/) returns the originally stored string value.

Note the library only supports UTF-8. When you store strings with different encodings in the library, calling [`dump()`](https://json.nlohmann.me/api/basic_json/dump/) may throw an exception unless `json::error_handler_t::replace` or `json::error_handler_t::ignore` are used as error handlers.

#### To/from streams (e.g., files, string streams)

You can also use streams to serialize and deserialize:

```cpp
// deserialize from standard input
json j;
std::cin >> j;

// serialize to standard output
std::cout << j;

// the setw manipulator was overloaded to set the indentation for pretty printing
std::cout << std::setw(4) << j << std::endl;
```

These operators work for any subclasses of `std::istream` or `std::ostream`. Here is the same example with files:

```cpp
// read a JSON file
std::ifstream i("file.json");
json j;
i >> j;

// write prettified JSON to another file
std::ofstream o("pretty.json");
o << std::setw(4) << j << std::endl;
```

Please note that setting the exception bit for `failbit` is inappropriate for this use case. It will result in program termination due to the `noexcept` specifier in use.

#### Read from iterator range

You can also parse JSON from an iterator range; that is, from any container accessible by iterators whose `value_type` is an integral type of 1, 2, or 4 bytes, which will be interpreted as UTF-8, UTF-16, and UTF-32 respectively. For instance, a `std::vector<std::uint8_t>`, or a `std::list<std::uint16_t>`:

```cpp
std::vector<std::uint8_t> v = {'t', 'r', 'u', 'e'};
json j = json::parse(v.begin(), v.end());
```

You may leave the iterators for the range [begin, end):

```cpp
std::vector<std::uint8_t> v = {'t', 'r', 'u', 'e'};
json j = json::parse(v);
```

#### Custom data source

Since the parse function accepts arbitrary iterator ranges, you can provide your own data sources by implementing the `LegacyInputIterator` concept.

```cpp
struct MyContainer {
  void advance();
  const char& get_current();
};

struct MyIterator {
    using difference_type = std::ptrdiff_t;
    using value_type = char;
    using pointer = const char*;
    using reference = const char&;
    using iterator_category = std::input_iterator_tag;

    explicit MyIterator(MyContainer* tgt = nullptr) : target(tgt) {}

    MyIterator& operator++() {
        target->advance();
        return *this;
    }

    bool operator!=(const MyIterator& rhs) const {
        return rhs.target != target;
    }

    reference operator*() const {
        return target->get_current();
    }

    MyContainer* target = nullptr;
};

MyIterator begin(MyContainer& tgt) {
    return MyIterator{&tgt};
}

MyIterator end(const MyContainer&) {
    return MyIterator{};
}

void foo() {
    MyContainer c;
    json j = json::parse(begin(c), end(c));
}
```

#### SAX interface

The library uses a SAX-like interface with the following functions:

```cpp
// called when null is parsed
bool null();

// called when a boolean is parsed; value is passed
bool boolean(bool val);

// called when a signed or unsigned integer number is parsed; value is passed
bool number_integer(number_integer_t val);
bool number_unsigned(number_unsigned_t val);

// called when a floating-point number is parsed; value and original string is passed
bool number_float(number_float_t val, const string_t& s);

// called when a string is parsed; value is passed and can be safely moved away
bool string(string_t& val);
// called when a binary value is parsed; value is passed and can be safely moved away
bool binary(binary_t& val);

// called when an object or array begins or ends, resp. The number of elements is passed (or -1 if not known)
bool start_object(std::size_t elements);
bool end_object();
bool start_array(std::size_t elements);
bool end_array();
// called when an object key is parsed; value is passed and can be safely moved away
bool key(string_t& val);

// called when a parse error occurs; byte position, the last token, and an exception is passed
bool parse_error(std::size_t position, const std::string& last_token, const detail::exception& ex);
```

The return value of each function determines whether parsing should proceed.

To implement your own SAX handler, proceed as follows:

1. Implement the SAX interface in a class. You can use class `nlohmann::json_sax<json>` as base class, but you can also use any class where the functions described above are implemented and public.
2. Create an object of your SAX interface class, e.g. `my_sax`.
3. Call `bool json::sax_parse(input, &my_sax)`; where the first parameter can be any input like a string or an input stream and the second parameter is a pointer to your SAX interface.

Note the `sax_parse` function only returns a `bool` indicating the result of the last executed SAX event. It does not return a  `json` value - it is up to you to decide what to do with the SAX events. Furthermore, no exceptions are thrown in case of a parse error -- it is up to you what to do with the exception object passed to your `parse_error` implementation. Internally, the SAX interface is used for the DOM parser (class `json_sax_dom_parser`) as well as the acceptor (`json_sax_acceptor`), see file [`json_sax.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/input/json_sax.hpp).

### STL-like access

We designed the JSON class to behave just like an STL container. In fact, it satisfies the [**ReversibleContainer**](https://en.cppreference.com/w/cpp/named_req/ReversibleContainer) requirement.

```cpp
// create an array using push_back
json j;
j.push_back("foo");
j.push_back(1);
j.push_back(true);

// also use emplace_back
j.emplace_back(1.78);

// iterate the array
for (json::iterator it = j.begin(); it != j.end(); ++it) {
  std::cout << *it << '\n';
}

// range-based for
for (auto& element : j) {
  std::cout << element << '\n';
}

// getter/setter
const auto tmp = j[0].get<std::string>();
j[1] = 42;
bool foo = j.at(2);

// comparison
j == R"(["foo", 1, true, 1.78])"_json;  // true

// other stuff
j.size();     // 4 entries
j.empty();    // false
j.type();     // json::value_t::array
j.clear();    // the array is empty again

// convenience type checkers
j.is_null();
j.is_boolean();
j.is_number();
j.is_object();
j.is_array();
j.is_string();

// create an object
json o;
o["foo"] = 23;
o["bar"] = false;
o["baz"] = 3.141;

// also use emplace
o.emplace("weather", "sunny");

// special iterator member functions for objects
for (json::iterator it = o.begin(); it != o.end(); ++it) {
  std::cout << it.key() << " : " << it.value() << "\n";
}

// the same code as range for
for (auto& el : o.items()) {
  std::cout << el.key() << " : " << el.value() << "\n";
}

// even easier with structured bindings (C++17)
for (auto& [key, value] : o.items()) {
  std::cout << key << " : " << value << "\n";
}

// find an entry
if (o.contains("foo")) {
  // there is an entry with key "foo"
}

// or via find and an iterator
if (o.find("foo") != o.end()) {
  // there is an entry with key "foo"
}

// or simpler using count()
int foo_present = o.count("foo"); // 1
int fob_present = o.count("fob"); // 0

// delete an entry
o.erase("foo");
```

### Conversion from STL containers

Any sequence container (`std::array`, `std::vector`, `std::deque`, `std::forward_list`, `std::list`) whose values can be used to construct JSON values (e.g., integers, floating point numbers, Booleans, string types, or again STL containers described in this section) can be used to create a JSON array. The same holds for similar associative containers (`std::set`, `std::multiset`, `std::unordered_set`, `std::unordered_multiset`), but in these cases the order of the elements of the array depends on how the elements are ordered in the respective STL container.

```cpp
std::vector c_vector {1, 2, 3, 4};
json j_vec(c_vector);
// [1, 2, 3, 4]

std::deque<double> c_deque {1.2, 2.3, 3.4, 5.6};
json j_deque(c_deque);
// [1.2, 2.3, 3.4, 5.6]

std::list c_list {true, true, false, true};
json j_list(c_list);
// [true, true, false, true]

std::forward_list c_flist {12345678909876, 23456789098765, 34567890987654, 45678909876543};
json j_flist(c_flist);
// [12345678909876, 23456789098765, 34567890987654, 45678909876543]

std::array c_array {{1, 2, 3, 4}};
json j_array(c_array);
// [1, 2, 3, 4]

std::set<std::string> c_set {"one", "two", "three", "four", "one"};
json j_set(c_set); // only one entry for "one" is used
// ["four", "one", "three", "two"]

std::unordered_set<std::string> c_uset {"one", "two", "three", "four", "one"};
json j_uset(c_uset); // only one entry for "one" is used
// maybe ["two", "three", "four", "one"]

std::multiset<std::string> c_mset {"one", "two", "one", "four"};
json j_mset(c_mset); // both entries for "one" are used
// maybe ["one", "two", "one", "four"]

std::unordered_multiset<std::string> c_umset {"one", "two", "one", "four"};
json j_umset(c_umset); // both entries for "one" are used
// maybe ["one", "two", "one", "four"]
```

Likewise, any associative key-value containers (`std::map`, `std::multimap`, `std::unordered_map`, `std::unordered_multimap`) whose keys can construct an `std::string` and whose values can be used to construct JSON values (see examples above) can be used to create a JSON object. Note that in case of multimaps, only one key is used in the JSON object and the value depends on the internal order of the STL container.

```cpp
std::map<std::string, int> c_map { {"one", 1}, {"two", 2}, {"three", 3} };
json j_map(c_map);
// {"one": 1, "three": 3, "two": 2 }

std::unordered_map<const char*, double> c_umap { {"one", 1.2}, {"two", 2.3}, {"three", 3.4} };
json j_umap(c_umap);
// {"one": 1.2, "two": 2.3, "three": 3.4}

std::multimap<std::string, bool> c_mmap { {"one", true}, {"two", true}, {"three", false}, {"three", true} };
json j_mmap(c_mmap); // only one entry for key "three" is used
// maybe {"one": true, "two": true, "three": true}

std::unordered_multimap<std::string, bool> c_ummap { {"one", true}, {"two", true}, {"three", false}, {"three", true} };
json j_ummap(c_ummap); // only one entry for key "three" is used
// maybe {"one": true, "two": true, "three": true}
```

### JSON Pointer and JSON Patch

The library supports **JSON Pointer** ([RFC 6901](https://tools.ietf.org/html/rfc6901)) as an alternative means to address structured values. On top of this, **JSON Patch** ([RFC 6902](https://tools.ietf.org/html/rfc6902)) allows describing differences between two JSON values -- effectively allowing patch and diff operations known from Unix.

```cpp
// a JSON value
json j_original = R"({
  "baz": ["one", "two", "three"],
  "foo": "bar"
})"_json;

// access members with a JSON pointer (RFC 6901)
j_original["/baz/1"_json_pointer];
// "two"

// a JSON patch (RFC 6902)
json j_patch = R"([
  { "op": "replace", "path": "/baz", "value": "boo" },
  { "op": "add", "path": "/hello", "value": ["world"] },
  { "op": "remove", "path": "/foo"}
])"_json;

// apply the patch
json j_result = j_original.patch(j_patch);
// {
//    "baz": "boo",
//    "hello": ["world"]
// }

// calculate a JSON patch from two JSON values
json::diff(j_result, j_original);
// [
//   { "op":" replace", "path": "/baz", "value": ["one", "two", "three"] },
//   { "op": "remove","path": "/hello" },
//   { "op": "add", "path": "/foo", "value": "bar" }
// ]
```

### JSON Merge Patch

The library supports **JSON Merge Patch** ([RFC 7386](https://tools.ietf.org/html/rfc7386)) as a patch format. Instead of using JSON Pointer (see above) to specify values to be manipulated, it describes the changes using a syntax that closely mimics the document being modified.

```cpp
// a JSON value
json j_document = R"({
  "a": "b",
  "c": {
    "d": "e",
    "f": "g"
  }
})"_json;

// a patch
json j_patch = R"({
  "a":"z",
  "c": {
    "f": null
  }
})"_json;

// apply the patch
j_document.merge_patch(j_patch);
// {
//  "a": "z",
//  "c": {
//    "d": "e"
//  }
// }
```

### Implicit conversions

Supported types can be implicitly converted to JSON values.

It is recommended to **NOT USE** implicit conversions **FROM** a JSON value.
You can find more details about this recommendation [here](https://www.github.com/nlohmann/json/issues/958).
You can switch off implicit conversions by defining `JSON_USE_IMPLICIT_CONVERSIONS` to `0` before including the `json.hpp` header. When using CMake, you can also achieve this by setting the option `JSON_ImplicitConversions` to `OFF`.

```cpp
// strings
std::string s1 = "Hello, world!";
json js = s1;
auto s2 = js.get<std::string>();
// NOT RECOMMENDED
std::string s3 = js;
std::string s4;
s4 = js;

// Booleans
bool b1 = true;
json jb = b1;
auto b2 = jb.get();
// NOT RECOMMENDED
bool b3 = jb;
bool b4;
b4 = jb;

// numbers
int i = 42;
json jn = i;
auto f = jn.get<double>();
// NOT RECOMMENDED
double f2 = jn;
double f3;
f3 = jn;

// etc.
```

Note that `char` types are not automatically converted to JSON strings, but to integer numbers. A conversion to a string must be specified explicitly:

```cpp
char ch = 'A';                       // ASCII value 65
json j_default = ch;                 // stores integer number 65
json j_string = std::string(1, ch);  // stores string "A"
```

### Arbitrary types conversions

Every type can be serialized in JSON, not just STL containers and scalar types. Usually, you would do something along those lines:

```cpp
namespace ns {
    // a simple struct to model a person
    struct person {
        std::string name;
        std::string address;
        int age;
    };
}

ns::person p = {"Ned Flanders", "744 Evergreen Terrace", 60};

// convert to JSON: copy each value into the JSON object
json j;
j["name"] = p.name;
j["address"] = p.address;
j["age"] = p.age;

// ...

// convert from JSON: copy each value from the JSON object
ns::person p {
    j["name"].get<std::string>(),
    j["address"].get<std::string>(),
    j["age"].get()
};
```

It works, but that's quite a lot of boilerplate... Fortunately, there's a better way:

```cpp
// create a person
ns::person p {"Ned Flanders", "744 Evergreen Terrace", 60};

// conversion: person -> json
json j = p;

std::cout << j << std::endl;
// {"address":"744 Evergreen Terrace","age":60,"name":"Ned Flanders"}

// conversion: json -> person
auto p2 = j.get<ns::person>();

// that's it
assert(p == p2);
```

#### Basic usage

To make this work with one of your types, you only need to provide two functions:

```cpp
using json = nlohmann::json;

namespace ns {
    void to_json(json& j, const person& p) {
        j = json{{"name", p.name}, {"address", p.address}, {"age", p.age}};
    }

    void from_json(const json& j, person& p) {
        j.at("name").get_to(p.name);
        j.at("address").get_to(p.address);
        j.at("age").get_to(p.age);
    }
} // namespace ns
```

That's all! When calling the `json` constructor with your type, your custom `to_json` method will be automatically called.
Likewise, when calling `get<your_type>()` or `get_to(your_type&)`, the `from_json` method will be called.

Some important things:

- Those methods **MUST** be in your type's namespace (which can be the global namespace), or the library will not be able to locate them (in this example, they are in namespace `ns`, where `person` is defined).
- Those methods **MUST** be available (e.g., proper headers must be included) everywhere you use these conversions. Look at [issue 1108](https://github.com/nlohmann/json/issues/1108) for errors that may occur otherwise.
- When using `get<your_type>()`, `your_type` **MUST** be [DefaultConstructible](https://en.cppreference.com/w/cpp/named_req/DefaultConstructible). (There is a way to bypass this requirement described later.)
- In function `from_json`, use function [`at()`](https://json.nlohmann.me/api/basic_json/at/) to access the object values rather than `operator[]`. In case a key does not exist, `at` throws an exception that you can handle, whereas `operator[]` exhibits undefined behavior.
- You do not need to add serializers or deserializers for STL types like `std::vector`: the library already implements these.

#### Simplify your life with macros

If you just want to serialize/deserialize some structs, the `to_json`/`from_json` functions can be a lot of boilerplate. There are [**several macros**](https://json.nlohmann.me/api/macros/#serializationdeserialization-macros) to make your life easier as long as you want to use a JSON object as serialization.

Which macro to choose depends on whether private member variables need to be accessed, a deserialization is needed, missing values should yield an error or should be replaced by default values, and if derived classes are used. See [this overview to choose the right one for your use case](https://json.nlohmann.me/features/arbitrary_types/#simplify-your-life-with-macros).

##### Example usage of macros

The `to_json`/`from_json` functions for the `person` struct above can be created with [`NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE`](https://json.nlohmann.me/api/macros/nlohmann_define_type_non_intrusive/). In all macros, the first parameter is the name of the class/struct, and all remaining parameters name the members.

```cpp
namespace ns {
    NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE(person, name, address, age)
}
```

If you want to inherit the `person` struct and add a field to it, it can be done with:

```cpp
namespace ns {
    struct person_derived : person {
        std::string email;
    };
    
    NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE(person_derived, person, email)
}
```

Here is another example with private members, where [`NLOHMANN_DEFINE_TYPE_INTRUSIVE`](https://json.nlohmann.me/api/macros/nlohmann_define_type_intrusive/) is needed:

```cpp
namespace ns {
    class address {
      private:
        std::string street;
        int housenumber;
        int postcode;
  
      public:
        NLOHMANN_DEFINE_TYPE_INTRUSIVE(address, street, housenumber, postcode)
    };
}
```

Or in case if you use some naming convention that you do not want to expose to JSON:

```cpp
namespace ns {
    class address {
      private:
        std::string m_street;
        int m_housenumber;
        int m_postcode;

      public:
        NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_NAMES(address, "street", m_street,
                                                           "housenumber", m_housenumber,
                                                           "postcode", m_postcode)
    };
}
```

#### How do I convert third-party types?

This requires a bit more advanced technique. But first, let's see how this conversion mechanism works:

The library uses **JSON Serializers** to convert types to JSON.
The default serializer for `nlohmann::json` is `nlohmann::adl_serializer` (ADL means [Argument-Dependent Lookup](https://en.cppreference.com/w/cpp/language/adl)).

It is implemented like this (simplified):

```cpp
template <typename T>
struct adl_serializer {
    static void to_json(json& j, const T& value) {
        // calls the "to_json" method in T's namespace
    }

    static void from_json(const json& j, T& value) {
        // same thing, but with the "from_json" method
    }
};
```

This serializer works fine when you have control over the type's namespace. However, what about `boost::optional` or `std::filesystem::path` (C++17)? Hijacking the `boost` namespace is pretty bad, and it's illegal to add something other than template specializations to `std`...

To solve this, you need to add a specialization of `adl_serializer` to the `nlohmann` namespace, here's an example:

```cpp
// partial specialization (full specialization works too)
namespace nlohmann {
    template <typename T>
    struct adl_serializer> {
        static void to_json(json& j, const boost::optional<T>& opt) {
            if (opt == boost::none) {
                j = nullptr;
            } else {
              j = *opt; // this will call adl_serializer<T>::to_json which will
                        // find the free function to_json in T's namespace!
            }
        }

        static void from_json(const json& j, boost::optional<T>& opt) {
            if (j.is_null()) {
                opt = boost::none;
            } else {
                opt = j.get<T>(); // same as above, but with
                                  // adl_serializer<T>::from_json
            }
        }
    };
}
```

#### How can I use `get()` for non-default constructible/non-copyable types?

There is a way if your type is [MoveConstructible](https://en.cppreference.com/w/cpp/named_req/MoveConstructible). You will need to specialize the `adl_serializer` as well, but with a special `from_json` overload:

```cpp
struct move_only_type {
    move_only_type() = delete;
    move_only_type(int ii): i(ii) {}
    move_only_type(const move_only_type&) = delete;
    move_only_type(move_only_type&&) = default;

    int i;
};

namespace nlohmann {
    template <>
    struct adl_serializer<move_only_type> {
        // note: the return type is no longer 'void', and the method only takes
        // one argument
        static move_only_type from_json(const json& j) {
            return {j.get()};
        }

        // Here's the catch! You must provide a to_json method! Otherwise, you
        // will not be able to convert move_only_type to json, since you fully
        // specialized adl_serializer on that type
        static void to_json(json& j, move_only_type t) {
            j = t.i;
        }
    };
}
```

#### Can I write my own serializer? (Advanced use)

Yes. You might want to take a look at [`unit-udt.cpp`](https://github.com/nlohmann/json/blob/develop/tests/src/unit-udt.cpp) in the test suite, to see a few examples.

If you write your own serializer, you'll need to do a few things:

- use a different `basic_json` alias than `nlohmann::json` (the last template parameter of `basic_json` is the `JSONSerializer`)
- use your `basic_json` alias (or a template parameter) in all your `to_json`/`from_json` methods
- use `nlohmann::to_json` and `nlohmann::from_json` when you need ADL

Here is an example, without simplifications, that only accepts types with a size <= 32, and uses ADL.

```cpp
// You should use void as a second template argument
// if you don't need compile-time checks on T
template<typename T, typename SFINAE = typename std::enable_if<sizeof(T) <= 32>::type>
struct less_than_32_serializer {
    template <typename BasicJsonType>
    static void to_json(BasicJsonType& j, T value) {
        // we want to use ADL, and call the correct to_json overload
        using nlohmann::to_json; // this method is called by adl_serializer,
                                 // this is where the magic happens
        to_json(j, value);
    }

    template <typename BasicJsonType>
    static void from_json(const BasicJsonType& j, T& value) {
        // same thing here
        using nlohmann::from_json;
        from_json(j, value);
    }
};
```

Be **very** careful when reimplementing your serializer, you can stack overflow if you don't pay attention:

```cpp
template <typename T, void>
struct bad_serializer
{
    template <typename BasicJsonType>
    static void to_json(BasicJsonType& j, const T& value) {
      // this calls BasicJsonType::json_serializer<T>::to_json(j, value)
      // if BasicJsonType::json_serializer == bad_serializer ... oops!
      j = value;
    }

    template <typename BasicJsonType>
    static void to_json(const BasicJsonType& j, T& value) {
      // this calls BasicJsonType::json_serializer<T>::from_json(j, value)
      // if BasicJsonType::json_serializer == bad_serializer ... oops!
      value = j.get<T>(); // oops!
    }
};
```

### Specializing enum conversion

By default, enum values are serialized to JSON as integers. In some cases, this could result in undesired behavior. If an enum is modified or re-ordered after data has been serialized to JSON, the later deserialized JSON data may be undefined or a different enum value than was originally intended.

It is possible to more precisely specify how a given enum is mapped to and from JSON as shown below:

```cpp
// example enum type declaration
enum TaskState {
    TS_STOPPED,
    TS_RUNNING,
    TS_COMPLETED,
    TS_INVALID=-1,
};

// map TaskState values to JSON as strings
NLOHMANN_JSON_SERIALIZE_ENUM( TaskState, {
    {TS_INVALID, nullptr},
    {TS_STOPPED, "stopped"},
    {TS_RUNNING, "running"},
    {TS_COMPLETED, "completed"},
})
```

The `NLOHMANN_JSON_SERIALIZE_ENUM()` macro declares a set of `to_json()` / `from_json()` functions for type `TaskState` while avoiding repetition and boilerplate serialization code.

**Usage:**

```cpp
// enum to JSON as string
json j = TS_STOPPED;
assert(j == "stopped");

// json string to enum
json j3 = "running";
assert(j3.get<TaskState>() == TS_RUNNING);

// undefined json value to enum (where the first map entry above is the default)
json jPi = 3.14;
assert(jPi.get<TaskState>() == TS_INVALID);
```

Just as in [Arbitrary Type Conversions](#arbitrary-types-conversions) above,

- `NLOHMANN_JSON_SERIALIZE_ENUM()` MUST be declared in your enum type's namespace (which can be the global namespace), or the library will not be able to locate it, and it will default to integer serialization.
- It MUST be available (e.g., proper headers must be included) everywhere you use the conversions.

Other Important points:

- When using `get<ENUM_TYPE>()`, undefined JSON values will default to the first pair specified in your map. Select this default pair carefully. If you desire an exception in this circumstance use `NLOHMANN_JSON_SERIALIZE_ENUM_STRICT()` which behaves identically except for throwing an exception on unrecognized values.
- If an enum or JSON value is specified more than once in your map, the first matching occurrence from the top of the map will be returned when converting to or from JSON.

### Binary formats (BSON, CBOR, MessagePack, UBJSON, and BJData)

Though JSON is a ubiquitous data format, it is not a very compact format suitable for data exchange, for instance over a network. Hence, the library supports [BSON](https://bsonspec.org) (Binary JSON), [CBOR](https://cbor.io) (Concise Binary Object Representation), [MessagePack](https://msgpack.org), [UBJSON](https://ubjson.org) (Universal Binary JSON Specification) and [BJData](https://neurojson.org/bjdata) (Binary JData) to efficiently encode JSON values to byte vectors and to decode such vectors.

```cpp
// create a JSON value
json j = R"({"compact": true, "schema": 0})"_json;

// serialize to BSON
std::vector<std::uint8_t> v_bson = json::to_bson(j);

// 0x1B, 0x00, 0x00, 0x00, 0x08, 0x63, 0x6F, 0x6D, 0x70, 0x61, 0x63, 0x74, 0x00, 0x01, 0x10, 0x73, 0x63, 0x68, 0x65, 0x6D, 0x61, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00

// roundtrip
json j_from_bson = json::from_bson(v_bson);

// serialize to CBOR
std::vector<std::uint8_t> v_cbor = json::to_cbor(j);

// 0xA2, 0x67, 0x63, 0x6F, 0x6D, 0x70, 0x61, 0x63, 0x74, 0xF5, 0x66, 0x73, 0x63, 0x68, 0x65, 0x6D, 0x61, 0x00

// roundtrip
json j_from_cbor = json::from_cbor(v_cbor);

// serialize to MessagePack
std::vector<std::uint8_t> v_msgpack = json::to_msgpack(j);

// 0x82, 0xA7, 0x63, 0x6F, 0x6D, 0x70, 0x61, 0x63, 0x74, 0xC3, 0xA6, 0x73, 0x63, 0x68, 0x65, 0x6D, 0x61, 0x00

// roundtrip
json j_from_msgpack = json::from_msgpack(v_msgpack);

// serialize to UBJSON
std::vector<std::uint8_t> v_ubjson = json::to_ubjson(j);

// 0x7B, 0x69, 0x07, 0x63, 0x6F, 0x6D, 0x70, 0x61, 0x63, 0x74, 0x54, 0x69, 0x06, 0x73, 0x63, 0x68, 0x65, 0x6D, 0x61, 0x69, 0x00, 0x7D

// roundtrip
json j_from_ubjson = json::from_ubjson(v_ubjson);
```

The library also supports binary types from BSON, CBOR (byte strings), and MessagePack (bin, ext, fixext). They are stored by default as `std::vector<std::uint8_t>` to be processed outside the library.

```cpp
// CBOR byte string with payload 0xCAFE
std::vector<std::uint8_t> v = {0x42, 0xCA, 0xFE};

// read value
json j = json::from_cbor(v);

// the JSON value has type binary
j.is_binary(); // true

// get reference to stored binary value
auto& binary = j.get_binary();

// the binary value has no subtype (CBOR has no binary subtypes)
binary.has_subtype(); // false

// access std::vector<std::uint8_t> member functions
binary.size(); // 2
binary[0]; // 0xCA
binary[1]; // 0xFE

// set subtype to 0x10
binary.set_subtype(0x10);

// serialize to MessagePack
auto cbor = json::to_msgpack(j); // 0xD5 (fixext2), 0x10, 0xCA, 0xFE
```

## Customers

The library is used in multiple projects, applications, operating systems, etc. The list below is not exhaustive, but the result of an internet search. If you know further customers of the library, please let me know, see [contact](#contact).

[](https://json.nlohmann.me/home/customers/)

## Ecosystem

Beyond projects that use the library, there are third-party projects that build on top of it - schema validators,
language bindings, format converters, and the like. See the curated [Ecosystem](https://json.nlohmann.me/community/ecosystem/) page.

## Supported compilers

Though it's 2026 already, the support for C++11 is still a bit sparse. Currently, the following compilers are known to work:

- GCC 4.8 - 14.2 (and possibly later)
- Clang 3.4 - 21.0 (and possibly later)
- Apple Clang 9.1 - 16.0 (and possibly later)
- Intel C++ Compiler 17.0.2 (and possibly later)
- Nvidia CUDA Compiler 11.0.221 (and possibly later)
- Microsoft Visual C++ 2015 / Build Tools 14.0.25123.0 (and possibly later)
- Microsoft Visual C++ 2017 / Build Tools 15.5.180.51428 (and possibly later)
- Microsoft Visual C++ 2019 / Build Tools 16.3.1+1def00d3d (and possibly later)
- Microsoft Visual C++ 2022 / Build Tools 19.30.30709.0 (and possibly later)

I would be happy to learn about other compilers/versions.

Please note:

- GCC 4.8 has a bug [57824](https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57824): multiline raw strings cannot be the arguments to macros. Don't use multiline raw strings directly in macros with this compiler.
- Android defaults to using very old compilers and C++ libraries. To fix this, add the following to your `Application.mk`. This will switch to the LLVM C++ library, the Clang compiler, and enable C++11 and other features disabled by default.

    ```makefile
    APP_STL := c++_shared
    NDK_TOOLCHAIN_VERSION := clang3.6
    APP_CPPFLAGS += -frtti -fexceptions
    ```

    The code compiles successfully with [Android NDK](https://developer.android.com/ndk/index.html?hl=ml), Revision 9 - 11 (and possibly later) and [CrystaX's Android NDK](https://www.crystax.net/en/android/ndk) version 10.

- For GCC running on MinGW or Android SDK, the error `'to_string' is not a member of 'std'` (or similarly, for `strtod` or `strtof`) may occur. Note this is not an issue with the code, but rather with the compiler itself. On Android, see above to build with a newer environment.  For MinGW, please refer to [this site](https://tehsausage.com/mingw-to-string) and [this discussion](https://github.com/nlohmann/json/issues/136) for information on how to fix this bug. For Android NDK using `APP_STL := gnustl_static`, please refer to [this discussion](https://github.com/nlohmann/json/issues/219).

- Unsupported versions of GCC and Clang are rejected by `#error` directives. This can be switched off by defining `JSON_SKIP_UNSUPPORTED_COMPILER_CHECK`. Note that you can expect no support in this case.

See the page [quality assurance](https://json.nlohmann.me/community/quality_assurance) on the compilers used to check the library in the CI.

## Integration

[`json.hpp`](https://github.com/nlohmann/json/blob/develop/single_include/nlohmann/json.hpp) is the single required file in `single_include/nlohmann` or [released here](https://github.com/nlohmann/json/releases). You need to add

```cpp
#include <nlohmann/json.hpp>

// for convenience
using json = nlohmann::json;
```

to the files you want to process JSON and set the necessary switches to enable C++11 (e.g., `-std=c++11` for GCC and Clang).

You can further use file [`include/nlohmann/json_fwd.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/json_fwd.hpp) for forward-declarations. The installation of `json_fwd.hpp` (as part of cmake's install step) can be achieved by setting `-DJSON_MultipleHeaders=ON`.

### CMake

You can also use the `nlohmann_json::nlohmann_json` interface target in CMake.  This target populates the appropriate usage requirements for `INTERFACE_INCLUDE_DIRECTORIES` to point to the appropriate include directories and `INTERFACE_COMPILE_FEATURES` for the necessary C++11 flags.

#### External

To use this library from a CMake project, you can locate it directly with `find_package()` and use the namespaced imported target from the generated package configuration:

```cmake
# CMakeLists.txt
find_package(nlohmann_json 3.12.0 REQUIRED)
...
add_library(foo ...)
...
target_link_libraries(foo PRIVATE nlohmann_json::nlohmann_json)
```

The package configuration file, `nlohmann_jsonConfig.cmake`, can be used either from an install tree or directly out of the build tree.

#### Embedded

To embed the library directly into an existing CMake project, place the entire source tree in a subdirectory and call `add_subdirectory()` in your `CMakeLists.txt` file:

```cmake
# Typically you don't care so much for a third party library's tests to be
# run from your own project's code.
set(JSON_BuildTests OFF CACHE INTERNAL "")

# If you only include this third party in PRIVATE source files, you do not
# need to install it when your main project gets installed.
# set(JSON_Install OFF CACHE INTERNAL "")

# Don't use include(nlohmann_json/CMakeLists.txt) since that carries with it
# unintended consequences that will break the build.  It's generally
# discouraged (although not necessarily well documented as such) to use
# include(...) for pulling in other CMake projects anyways.
add_subdirectory(nlohmann_json)
...
add_library(foo ...)
...
target_link_libraries(foo PRIVATE nlohmann_json::nlohmann_json)
```

##### Embedded (FetchContent)

Since CMake v3.11,
[FetchContent](https://cmake.org/cmake/help/v3.11/module/FetchContent.html) can
be used to automatically download a release as a dependency at configure time.

Example:

```cmake
include(FetchContent)

FetchContent_Declare(json URL https://github.com/nlohmann/json/releases/download/v3.12.0/json.tar.xz)
FetchContent_MakeAvailable(json)

target_link_libraries(foo PRIVATE nlohmann_json::nlohmann_json)
```

**Note**: It is recommended to use the URL approach described above, which is supported as of version 3.10.0. See
<https://json.nlohmann.me/integration/cmake/#fetchcontent> for more information.

#### Supporting Both

To allow your project to support either an externally supplied or an embedded JSON library, you can use a pattern akin to the following:

``` cmake
# Top level CMakeLists.txt
project(FOO)
...
option(FOO_USE_EXTERNAL_JSON "Use an external JSON library" OFF)
...
add_subdirectory(thirdparty)
...
add_library(foo ...)
...
# Note that the namespaced target will always be available regardless of the
# import method
target_link_libraries(foo PRIVATE nlohmann_json::nlohmann_json)
```

```cmake
# thirdparty/CMakeLists.txt
...
if(FOO_USE_EXTERNAL_JSON)
  find_package(nlohmann_json 3.12.0 REQUIRED)
else()
  set(JSON_BuildTests OFF CACHE INTERNAL "")
  add_subdirectory(nlohmann_json)
endif()
...
```

`thirdparty/nlohmann_json` is then a complete copy of this source tree.

### Package Managers

Use your favorite [**package manager**](https://json.nlohmann.me/integration/package_managers/) to use the library.

- &nbsp;[**Homebrew**](https://json.nlohmann.me/integration/package_managers/#homebrew) `nlohmann-json`
- &nbsp;[**Meson**](https://json.nlohmann.me/integration/package_managers/#meson) `nlohmann_json`
- &nbsp;[**Bazel**](https://json.nlohmann.me/integration/package_managers/#bazel) `nlohmann_json`
- &nbsp;[**Conan**](https://json.nlohmann.me/integration/package_managers/#conan) `nlohmann_json`
- &nbsp;[**Spack**](https://json.nlohmann.me/integration/package_managers/#spack) `nlohmann-json`
- [**Hunter**](https://json.nlohmann.me/integration/package_managers/#hunter) `nlohmann_json`
- &nbsp;[**vcpkg**](https://json.nlohmann.me/integration/package_managers/#vcpkg) `nlohmann-json`
- [**cget**](https://json.nlohmann.me/integration/package_managers/#cget) `nlohmann/json`
- &nbsp;[**Swift Package Manager**](https://json.nlohmann.me/integration/package_managers/#swift-package-manager) `nlohmann/json`
- &nbsp;[**Nuget**](https://json.nlohmann.me/integration/package_managers/#nuget) `nlohmann.json`
- &nbsp;[**Conda**](https://json.nlohmann.me/integration/package_managers/#conda) `nlohmann_json`
- &nbsp;[**MacPorts**](https://json.nlohmann.me/integration/package_managers/#macports) `nlohmann-json`
- &nbsp;[**cpm.cmake**](https://json.nlohmann.me/integration/package_managers/#cpmcmake) `gh:nlohmann/json`
- &nbsp;[**xmake**](https://json.nlohmann.me/integration/package_managers/#xmake) `nlohmann_json`

The library is part of many package managers. See the [**documentation**](https://json.nlohmann.me/integration/package_managers/) for detailed descriptions and examples.

### Pkg-config

If you are using bare Makefiles, you can use `pkg-config` to generate the include flags that point to where the library is installed:

```sh
pkg-config nlohmann_json --cflags
```

## License



The class is licensed under the [MIT License](https://opensource.org/licenses/MIT):

Copyright &copy; 2013-2026 [Niels Lohmann](https://nlohmann.me)

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

* * *

- The class contains the UTF-8 Decoder from Bjoern Hoehrmann which is licensed under the [MIT License](https://opensource.org/licenses/MIT) (see above). Copyright &copy; 2008-2009 [Björn Hoehrmann](https://bjoern.hoehrmann.de/) 
- The class contains a slightly modified version of the Grisu2 algorithm from Florian Loitsch which is licensed under the [MIT License](https://opensource.org/licenses/MIT) (see above). Copyright &copy; 2009 [Florian Loitsch](https://florian.loitsch.com/)
- The class contains a copy of [Hedley](https://nemequ.github.io/hedley/) from Evan Nemerson which is licensed as [CC0-1.0](https://creativecommons.org/publicdomain/zero/1.0/).
- The class contains parts of [Google Abseil](https://github.com/abseil/abseil-cpp) which is licensed under the [Apache 2.0 License](https://opensource.org/licenses/Apache-2.0).



The library is compliant to version 3.3 of the [**REUSE specification**](https://reuse.software):

- Every source file contains an SPDX copyright header.
- The full text of all licenses used in the repository can be found in the `LICENSES` folder.
- File `.reuse/dep5` contains an overview of all files' copyrights and licenses.
- Run `pipx run reuse lint` to verify the project's REUSE compliance and `pipx run reuse spdx` to generate a SPDX SBOM.

## Contact

If you have questions regarding the library, I would like to invite you to [open an issue at GitHub](https://github.com/nlohmann/json/issues/new/choose). Please describe your request, problem, or question as detailed as possible, and also mention the version of the library you are using as well as the version of your compiler and operating system. Opening an issue at GitHub allows other users and contributors to this library to collaborate. For instance, I have little experience with MSVC, and most issues in this regard have been solved by a growing community. If you have a look at the [closed issues](https://github.com/nlohmann/json/issues?q=is%3Aissue+is%3Aclosed), you will see that we react quite timely in most cases.

Only if your request would contain confidential information, please [send me an email](mailto:mail@nlohmann.me). For encrypted messages, please use [this key](https://keybase.io/nlohmann/pgp_keys.asc).

## Security

[Commits by Niels Lohmann](https://github.com/nlohmann/json/commits) and [releases](https://github.com/nlohmann/json/releases) are signed with this [PGP Key](https://keybase.io/nlohmann/pgp_keys.asc?fingerprint=797167ae41c0a6d9232e48457f3cea63ae251b69).

## Thanks

I deeply appreciate the help of the following people.



1. [Teemperor](https://github.com/Teemperor) implemented CMake support and lcov integration, realized escape and Unicode handling in the string parser, and fixed the JSON serialization.
2. [elliotgoodrich](https://github.com/elliotgoodrich) fixed an issue with double deletion in the iterator classes.
3. [kirkshoop](https://github.com/kirkshoop) made the iterators of the class composable to other libraries.
4. [wancw](https://github.com/wanwc) fixed a bug that hindered the class to compile with Clang.
5. Tomas Åblad found a bug in the iterator implementation.
6. [Joshua C. Randall](https://github.com/jrandall) fixed a bug in the floating-point serialization.
7. [Aaron Burghardt](https://github.com/aburgh) implemented code to parse streams incrementally. Furthermore, he greatly improved the parser class by allowing the definition of a filter function to discard undesired elements while parsing.
8. [Daniel Kopeček](https://github.com/dkopecek) fixed a bug in the compilation with GCC 5.0.
9. [Florian Weber](https://github.com/Florianjw) fixed a bug in and improved the performance of the comparison operators.
10. [Eric Cornelius](https://github.com/EricMCornelius) pointed out a bug in the handling with NaN and infinity values. He also improved the performance of the string escaping.
11. [易思龙](https://github.com/likebeta) implemented a conversion from anonymous enums.
12. [kepkin](https://github.com/kepkin) patiently pushed forward the support for Microsoft Visual Studio.
13. [gregmarr](https://github.com/gregmarr) simplified the implementation of reverse iterators and helped with numerous hints and improvements. In particular, he pushed forward the implementation of user-defined types.
14. [Caio Luppi](https://github.com/caiovlp) fixed a bug in the Unicode handling.
15. [dariomt](https://github.com/dariomt) fixed some typos in the examples.
16. [Daniel Frey](https://github.com/d-frey) cleaned up some pointers and implemented exception-safe memory allocation.
17. [Colin Hirsch](https://github.com/ColinH) took care of a small namespace issue.
18. [Huu Nguyen](https://github.com/whoshuu) corrected a variable name in the documentation.
19. [Silverweed](https://github.com/silverweed) overloaded `parse()` to accept an rvalue reference.
20. [dariomt](https://github.com/dariomt) fixed a subtlety in MSVC type support and implemented the `get_ref()` function to get a reference to stored values.
21. [ZahlGraf](https://github.com/ZahlGraf) added a workaround that allows compilation using Android NDK.
22. [whackashoe](https://github.com/whackashoe) replaced a function that was marked as unsafe by Visual Studio.
23. [406345](https://github.com/406345) fixed two small warnings.
24. [Glen Fernandes](https://github.com/glenfe) noted a potential portability problem in the `has_mapped_type` function.
25. [Corbin Hughes](https://github.com/nibroc) fixed some typos in the contribution guidelines.
26. [twelsby](https://github.com/twelsby) fixed the array subscript operator, an issue that failed the MSVC build, and floating-point parsing/dumping. He further added support for unsigned integer numbers and implemented better roundtrip support for parsed numbers.
27. [Volker Diels-Grabsch](https://github.com/vog) fixed a link in the README file.
28. [msm-](https://github.com/msm-) added support for American Fuzzy Lop.
29. [Annihil](https://github.com/Annihil) fixed an example in the README file.
30. [Themercee](https://github.com/Themercee) noted a wrong URL in the README file.
31. [Lv Zheng](https://github.com/lv-zheng) fixed a namespace issue with `int64_t` and `uint64_t`.
32. [abc100m](https://github.com/abc100m) analyzed the issues with GCC 4.8 and proposed a [partial solution](https://github.com/nlohmann/json/pull/212).
33. [zewt](https://github.com/zewt) added useful notes to the README file about Android.
34. [Róbert Márki](https://github.com/robertmrk) added a fix to use move iterators and improved the integration via CMake.
35. [Chris Kitching](https://github.com/ChrisKitching) cleaned up the CMake files.
36. [Tom Needham](https://github.com/06needhamt) fixed a subtle bug with MSVC 2015 which was also proposed by [Michael K.](https://github.com/Epidal).
37. [Mário Feroldi](https://github.com/thelostt) fixed a small typo.
38. [duncanwerner](https://github.com/duncanwerner) found a really embarrassing performance regression in the 2.0.0 release.
39. [Damien](https://github.com/dtoma) fixed one of the last conversion warnings.
40. [Thomas Braun](https://github.com/t-b) fixed a warning in a test case and adjusted MSVC calls in the CI.
41. [Théo DELRIEU](https://github.com/theodelrieu) patiently and constructively oversaw the long way toward [iterator-range parsing](https://github.com/nlohmann/json/issues/290). He also implemented the magic behind the serialization/deserialization of user-defined types and split the single header file into smaller chunks.
42. [Stefan](https://github.com/5tefan) fixed a minor issue in the documentation.
43. [Vasil Dimov](https://github.com/vasild) fixed the documentation regarding conversions from `std::multiset`.
44. [ChristophJud](https://github.com/ChristophJud) overworked the CMake files to ease project inclusion.
45. [Vladimir Petrigo](https://github.com/vpetrigo) made a SFINAE hack more readable and added Visual Studio 17 to the build matrix.
46. [Denis Andrejew](https://github.com/seeekr) fixed a grammar issue in the README file.
47. [Pierre-Antoine Lacaze](https://github.com/palacaze) found a subtle bug in the `dump()` function.
48. [TurpentineDistillery](https://github.com/TurpentineDistillery) pointed to [`std::locale::classic()`](https://en.cppreference.com/w/cpp/locale/locale/classic) to avoid too much locale joggling, found some nice performance improvements in the parser, improved the benchmarking code, and realized locale-independent number parsing and printing.
49. [cgzones](https://github.com/cgzones) had an idea how to fix the Coverity scan.
50. [Jared Grubb](https://github.com/jaredgrubb) silenced a nasty documentation warning.
51. [Yixin Zhang](https://github.com/qwename) fixed an integer overflow check.
52. [Bosswestfalen](https://github.com/Bosswestfalen) merged two iterator classes into a smaller one.
53. [Daniel599](https://github.com/Daniel599) helped to get Travis to execute the tests with Clang's sanitizers.
54. [Jonathan Lee](https://github.com/vjon) fixed an example in the README file.
55. [gnzlbg](https://github.com/gnzlbg) supported the implementation of user-defined types.
56. [Alexej Harm](https://github.com/qis) helped to get the user-defined types working with Visual Studio.
57. [Jared Grubb](https://github.com/jaredgrubb) supported the implementation of user-defined types.
58. [EnricoBilla](https://github.com/EnricoBilla) noted a typo in an example.
59. [Martin Hořeňovský](https://github.com/horenmar) found a way for a 2x speedup for the compilation time of the test suite.
60. [ukhegg](https://github.com/ukhegg) proposed an improvement for the examples section.
61. [rswanson-ihi](https://github.com/rswanson-ihi) noted a typo in the README.
62. [Mihai Stan](https://github.com/stanmihai4) fixed a bug in the comparison with `nullptr`s.
63. [Tushar Maheshwari](https://github.com/tusharpm) added [cotire](https://github.com/sakra/cotire) support to speed up the compilation.
64. [TedLyngmo](https://github.com/TedLyngmo) noted a typo in the README, removed unnecessary bit arithmetic, and fixed some `-Weffc++` warnings.
65. [Krzysztof Woś](https://github.com/krzysztofwos) made exceptions more visible.
66. [ftillier](https://github.com/ftillier) fixed a compiler warning.
67. [tinloaf](https://github.com/tinloaf) made sure all pushed warnings are properly popped.
68. [Fytch](https://github.com/Fytch) found a bug in the documentation.
69. [Jay Sistar](https://github.com/Type1J) implemented a Meson build description.
70. [Henry Lee](https://github.com/HenryRLee) fixed a warning in ICC and improved the iterator implementation.
71. [Vincent Thiery](https://github.com/vthiery) maintains a package for the Conan package manager.
72. [Steffen](https://github.com/koemeet) fixed a potential issue with MSVC and `std::min`.
73. [Mike Tzou](https://github.com/Chocobo1) fixed some typos.
74. [amrcode](https://github.com/amrcode) noted misleading documentation about comparison of floats.
75. [Oleg Endo](https://github.com/olegendo) reduced the memory consumption by replacing `` with ``.
76. [dan-42](https://github.com/dan-42) cleaned up the CMake files to simplify including/reusing of the library.
77. [Nikita Ofitserov](https://github.com/himikof) allowed for moving values from initializer lists.
78. [Greg Hurrell](https://github.com/wincent) fixed a typo.
79. [Dmitry Kukovinets](https://github.com/DmitryKuk) fixed a typo.
80. [kbthomp1](https://github.com/kbthomp1) fixed an issue related to the Intel OSX compiler.
81. [Markus Werle](https://github.com/daixtrose) fixed a typo.
82. [WebProdPP](https://github.com/WebProdPP) fixed a subtle error in a precondition check.
83. [Alex](https://github.com/leha-bot) noted an error in a code sample.
84. [Tom de Geus](https://github.com/tdegeus) reported some warnings with ICC and helped to fix them.
85. [Perry Kundert](https://github.com/pjkundert) simplified reading from input streams.
86. [Sonu Lohani](https://github.com/sonulohani) fixed a small compilation error.
87. [Jamie Seward](https://github.com/jseward) fixed all MSVC warnings.
88. [Nate Vargas](https://github.com/eld00d) added a Doxygen tag file.
89. [pvleuven](https://github.com/pvleuven) helped to fix a warning in ICC.
90. [Pavel](https://github.com/crea7or) helped to fix some warnings in MSVC.
91. [Jamie Seward](https://github.com/jseward) avoided unnecessary string copies in `find()` and `count()`.
92. [Mitja](https://github.com/Itja) fixed some typos.
93. [Jorrit Wronski](https://github.com/jowr) updated the Hunter package links.
94. [Matthias Möller](https://github.com/TinyTinni) added a `.natvis` for the MSVC debug view.
95. [bogemic](https://github.com/bogemic) fixed some C++17 deprecation warnings.
96. [Eren Okka](https://github.com/erengy) fixed some MSVC warnings.
97. [abolz](https://github.com/abolz) integrated the Grisu2 algorithm for proper floating-point formatting, allowing more roundtrip checks to succeed.
98. [Vadim Evard](https://github.com/Pipeliner) fixed a Markdown issue in the README.
99. [zerodefect](https://github.com/zerodefect) fixed a compiler warning.
100. [Kert](https://github.com/kaidokert) allowed to template the string type in the serialization and added the possibility to override the exceptional behavior.
101. [mark-99](https://github.com/mark-99) helped fix an ICC error.
102. [Patrik Huber](https://github.com/patrikhuber) fixed links in the README file.
103. [johnfb](https://github.com/johnfb) found a bug in the implementation of CBOR's indefinite length strings.
104. [Paul Fultz II](https://github.com/pfultz2) added a note on the cget package manager.
105. [Wilson Lin](https://github.com/wla80) made the integration section of the README more concise.
106. [RalfBielig](https://github.com/ralfbielig) detected and fixed a memory leak in the parser callback.
107. [agrianius](https://github.com/agrianius) allowed dumping JSON to an alternative string type.
108. [Kevin Tonon](https://github.com/ktonon) overworked the C++11 compiler checks in CMake.
109. [Axel Huebl](https://github.com/ax3l) simplified a CMake check and added support for the [Spack package manager](https://spack.io).
110. [Carlos O'Ryan](https://github.com/coryan) fixed a typo.
111. [James Upjohn](https://github.com/jammehcow) fixed a version number in the compilers section.
112. [Chuck Atkins](https://github.com/chuckatkins) adjusted the CMake files to the CMake packaging guidelines and provided documentation for the CMake integration.
113. [Jan Schöppach](https://github.com/dns13) fixed a typo.
114. [martin-mfg](https://github.com/martin-mfg) fixed a typo.
115. [Matthias Möller](https://github.com/TinyTinni) removed the dependency from `std::stringstream`.
116. [agrianius](https://github.com/agrianius) added code to use alternative string implementations.
117. [Daniel599](https://github.com/Daniel599) allowed to use more algorithms with the `items()` function.
118. [Julius Rakow](https://github.com/jrakow) fixed the Meson include directory and fixed the links to [cppreference.com](https://cppreference.com).
119. [Sonu Lohani](https://github.com/sonulohani) fixed the compilation with MSVC 2015 in debug mode.
120. [grembo](https://github.com/grembo) fixed the test suite and re-enabled several test cases.
121. [Hyeon Kim](https://github.com/simnalamburt) introduced the macro `JSON_INTERNAL_CATCH` to control the exception handling inside the library.
122. [thyu](https://github.com/thyu) fixed a compiler warning.
123. [David Guthrie](https://github.com/LEgregius) fixed a subtle compilation error with Clang 3.4.2.
124. [Dennis Fischer](https://github.com/dennisfischer) allowed to call `find_package` without installing the library.
125. [Hyeon Kim](https://github.com/simnalamburt) fixed an issue with a double macro definition.
126. [Ben Berman](https://github.com/rivertam) made some error messages more understandable.
127. [zakalibit](https://github.com/zakalibit) fixed a compilation problem with the Intel C++ compiler.
128. [mandreyel](https://github.com/mandreyel) fixed a compilation problem.
129. [Kostiantyn Ponomarenko](https://github.com/koponomarenko) added version and license information to the Meson build file.
130. [Henry Schreiner](https://github.com/henryiii) added support for GCC 4.8.
131. [knilch](https://github.com/knilch0r) made sure the test suite does not stall when run in the wrong directory.
132. [Antonio Borondo](https://github.com/antonioborondo) fixed an MSVC 2017 warning.
133. [Dan Gendreau](https://github.com/dgendreau) implemented the `NLOHMANN_JSON_SERIALIZE_ENUM` macro to quickly define an enum/JSON mapping.
134. [efp](https://github.com/efp) added line and column information to parse errors.
135. [julian-becker](https://github.com/julian-becker) added BSON support.
136. [Pratik Chowdhury](https://github.com/pratikpc) added support for structured bindings.
137. [David Avedissian](https://github.com/davedissian) added support for Clang 5.0.1 (PS4 version).
138. [Jonathan Dumaresq](https://github.com/dumarjo) implemented an input adapter to read from `FILE*`.
139. [kjpus](https://github.com/kjpus) fixed a link in the documentation.
140. [Manvendra Singh](https://github.com/manu-chroma) fixed a typo in the documentation.
141. [ziggurat29](https://github.com/ziggurat29) fixed an MSVC warning.
142. [Sylvain Corlay](https://github.com/SylvainCorlay) added code to avoid an issue with MSVC.
143. [mefyl](https://github.com/mefyl) fixed a bug when JSON was parsed from an input stream.
144. [Millian Poquet](https://github.com/mpoquet) allowed to install the library via Meson.
145. [Michael Behrns-Miller](https://github.com/moodboom) found an issue with a missing namespace.
146. [Nasztanovics Ferenc](https://github.com/naszta) fixed a compilation issue with libc 2.12.
147. [Andreas Schwab](https://github.com/andreas-schwab) fixed the endian conversion.
148. [Mark-Dunning](https://github.com/Mark-Dunning) fixed a warning in MSVC.
149. [Gareth Sylvester-Bradley](https://github.com/garethsb-sony) added `operator/` for JSON Pointers.
150. [John-Mark](https://github.com/johnmarkwayve) noted a missing header.
151. [Vitaly Zaitsev](https://github.com/xvitaly) fixed compilation with GCC 9.0.
152. [Laurent Stacul](https://github.com/stac47) fixed compilation with GCC 9.0.
153. [Ivor Wanders](https://github.com/iwanders) helped to reduce the CMake requirement to version 3.1.
154. [njlr](https://github.com/njlr) updated the Buckaroo instructions.
155. [Lion](https://github.com/lieff) fixed a compilation issue with GCC 7 on CentOS.
156. [Isaac Nickaein](https://github.com/nickaein) improved the integer serialization performance and implemented the `contains()` function.
157. [past-due](https://github.com/past-due) suppressed an unfixable warning.
158. [Elvis Oric](https://github.com/elvisoric) improved Meson support.
159. [Matěj Plch](https://github.com/Afforix) fixed an example in the README.
160. [Mark Beckwith](https://github.com/wythe) fixed a typo.
161. [scinart](https://github.com/scinart) fixed a bug in the serializer.
162. [Patrick Boettcher](https://github.com/pboettch) implemented `push_back()` and `pop_back()` for JSON Pointers.
163. [Bruno Oliveira](https://github.com/nicoddemus) added support for Conda.
164. [Michele Caini](https://github.com/skypjack) fixed links in the README.
165. [Hani](https://github.com/hnkb) documented how to install the library with NuGet.
166. [Mark Beckwith](https://github.com/wythe) fixed a typo.
167. [yann-morin-1998](https://github.com/yann-morin-1998) helped to reduce the CMake requirement to version 3.1.
168. [Konstantin Podsvirov](https://github.com/podsvirov) maintains a package for the MSYS2 software distro.
169. [remyabel](https://github.com/remyabel) added GNUInstallDirs to the CMake files.
170. [Taylor Howard](https://github.com/taylorhoward92) fixed a unit test.
171. [Gabe Ron](https://github.com/Macr0Nerd) implemented the `to_string` method.
172. [Watal M. Iwasaki](https://github.com/heavywatal) fixed a Clang warning.
173. [Viktor Kirilov](https://github.com/onqtam) switched the unit tests from [Catch](https://github.com/philsquared/Catch) to [doctest](https://github.com/onqtam/doctest)
174. [Juncheng E](https://github.com/ejcjason) fixed a typo.
175. [tete17](https://github.com/tete17) fixed a bug in the `contains` function.
176. [Xav83](https://github.com/Xav83) fixed some cppcheck warnings.
177. [0xflotus](https://github.com/0xflotus) fixed some typos.
178. [Christian Deneke](https://github.com/chris0x44) added a const version of `json_pointer::back`.
179. [Julien Hamaide](https://github.com/crazyjul) made the `items()` function work with custom string types.
180. [Evan Nemerson](https://github.com/nemequ) updated fixed a bug in Hedley and updated this library accordingly.
181. [Florian Pigorsch](https://github.com/flopp) fixed a lot of typos.
182. [Camille Bégué](https://github.com/cbegue) fixed an issue in the conversion from  `std::pair` and `std::tuple` to `json`.
183. [Anthony VH](https://github.com/AnthonyVH) fixed a compile error in an enum deserialization.
184. [Yuriy Vountesmery](https://github.com/ua-code-dragon) noted a subtle bug in a preprocessor check.
185. [Chen](https://github.com/dota17) fixed numerous issues in the library.
186. [Antony Kellermann](https://github.com/aokellermann) added a CI step for GCC 10.1.
187. [Alex](https://github.com/gistrec) fixed an MSVC warning.
188. [Rainer](https://github.com/rvjr) proposed an improvement in the floating-point serialization in CBOR.
189. [Francois Chabot](https://github.com/FrancoisChabot) made performance improvements in the input adapters.
190. [Arthur Sonzogni](https://github.com/ArthurSonzogni) documented how the library can be included via `FetchContent`.
191. [Rimas Misevičius](https://github.com/rmisev) fixed an error message.
192. [Alexander Myasnikov](https://github.com/alexandermyasnikov) fixed some examples and a link in the README.
193. [Hubert Chathi](https://github.com/uhoreg) made CMake's version config file architecture-independent.
194. [OmnipotentEntity](https://github.com/OmnipotentEntity) implemented the binary values for CBOR, MessagePack, BSON, and UBJSON.
195. [ArtemSarmini](https://github.com/ArtemSarmini) fixed a compilation issue with GCC 10 and fixed a leak.
196. [Evgenii Sopov](https://github.com/sea-kg) integrated the library to the wsjcpp package manager.
197. [Sergey Linev](https://github.com/linev) fixed a compiler warning.
198. [Miguel Magalhães](https://github.com/magamig) fixed the year in the copyright.
199. [Gareth Sylvester-Bradley](https://github.com/garethsb-sony) fixed a compilation issue with MSVC.
200. [Alexander “weej” Jones](https://github.com/alex-weej) fixed an example in the README.
201. [Antoine Cœur](https://github.com/Coeur) fixed some typos in the documentation.
202. [jothepro](https://github.com/jothepro) updated links to the Hunter package.
203. [Dave Lee](https://github.com/kastiglione) fixed a link in the README.
204. [Joël Lamotte](https://github.com/Klaim) added instruction for using Build2's package manager.
205. [Paul Jurczak](https://github.com/pauljurczak) fixed an example in the README.
206. [Sonu Lohani](https://github.com/sonulohani) fixed a warning.
207. [Carlos Gomes Martinho](https://github.com/gocarlos) updated the Conan package source.
208. [Konstantin Podsvirov](https://github.com/podsvirov) fixed the MSYS2 package documentation.
209. [Tridacnid](https://github.com/Tridacnid) improved the CMake tests.
210. [Michael](https://github.com/MBalszun) fixed MSVC warnings.
211. [Quentin Barbarat](https://github.com/quentin-dev) fixed an example in the documentation.
212. [XyFreak](https://github.com/XyFreak) fixed a compiler warning.
213. [TotalCaesar659](https://github.com/TotalCaesar659) fixed links in the README.
214. [Tanuj Garg](https://github.com/tanuj208) improved the fuzzer coverage for UBSAN input.
215. [AODQ](https://github.com/AODQ) fixed a compiler warning.
216. [jwittbrodt](https://github.com/jwittbrodt) made `NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE` inline.
217. [pfeatherstone](https://github.com/pfeatherstone) improved the upper bound of arguments of the `NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE`/`NLOHMANN_DEFINE_TYPE_INTRUSIVE` macros.
218. [Jan Procházka](https://github.com/jprochazk) fixed a bug in the CBOR parser for binary and string values.
219. [T0b1-iOS](https://github.com/T0b1-iOS) fixed a bug in the new hash implementation.
220. [Matthew Bauer](https://github.com/matthewbauer) adjusted the CBOR writer to create tags for binary subtypes.
221. [gatopeich](https://github.com/gatopeich) implemented an ordered map container for `nlohmann::ordered_json`.
222. [Érico Nogueira Rolim](https://github.com/ericonr) added support for pkg-config.
223. [KonanM](https://github.com/KonanM) proposed an implementation for the `NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE`/`NLOHMANN_DEFINE_TYPE_INTRUSIVE` macros.
224. [Guillaume Racicot](https://github.com/gracicot) implemented `string_view` support and allowed C++20 support.
225. [Alex Reinking](https://github.com/alexreinking) improved CMake support for `FetchContent`.
226. [Hannes Domani](https://github.com/ssbssa) provided a GDB pretty printer.
227. Lars Wirzenius reviewed the README file.
228. [Jun Jie](https://github.com/ongjunjie) fixed a compiler path in the CMake scripts.
229. [Ronak Buch](https://github.com/rbuch) fixed typos in the documentation.
230. [Alexander Karzhenkov](https://github.com/karzhenkov) fixed a move constructor and the Travis builds.
231. [Leonardo Lima](https://github.com/leozz37) added CPM.Cmake support.
232. [Joseph Blackman](https://github.com/jbzdarkid) fixed a warning.
233. [Yaroslav](https://github.com/YarikTH) updated doctest and implemented unit tests.
234. [Martin Stump](https://github.com/globberwops) fixed a bug in the CMake files.
235. [Jaakko Moisio](https://github.com/jasujm) fixed a bug in the input adapters.
236. [bl-ue](https://github.com/bl-ue) fixed some Markdown issues in the README file.
237. [William A. Wieselquist](https://github.com/wawiesel) fixed an example from the README.
238. [abbaswasim](https://github.com/abbaswasim) fixed an example from the README.
239. [Remy Jette](https://github.com/remyjette) fixed a warning.
240. [Fraser](https://github.com/frasermarlow) fixed the documentation.
241. [Ben Beasley](https://github.com/musicinmybrain) updated doctest.
242. [Doron Behar](https://github.com/doronbehar) fixed pkg-config.pc.
243. [raduteo](https://github.com/raduteo) fixed a warning.
244. [David Pfahler](https://github.com/theShmoo) added the possibility to compile the library without I/O support.
245. [Morten Fyhn Amundsen](https://github.com/mortenfyhn) fixed a typo.
246. [jpl-mac](https://github.com/jpl-mac) allowed treating the library as a system header in CMake.
247. [Jason Dsouza](https://github.com/jasmcaus) fixed the indentation of the CMake file.
248. [offa](https://github.com/offa) added a link to Conan Center to the documentation.
249. [TotalCaesar659](https://github.com/TotalCaesar659) updated the links in the documentation to use HTTPS.
250. [Rafail Giavrimis](https://github.com/grafail) fixed the Google Benchmark default branch.
251. [Louis Dionne](https://github.com/ldionne) fixed a conversion operator.
252. [justanotheranonymoususer](https://github.com/justanotheranonymoususer) made the examples in the README more consistent.
253. [Finkman](https://github.com/Finkman) suppressed some `-Wfloat-equal` warnings.
254. [Ferry Huberts](https://github.com/fhuberts) fixed `-Wswitch-enum` warnings.
255. [Arseniy Terekhin](https://github.com/senyai) made the GDB pretty-printer robust against unset variable names.
256. [Amir Masoud Abdol](https://github.com/amirmasoudabdol) updated the Homebrew command as nlohmann/json is now in homebrew-core.
257. [Hallot](https://github.com/Hallot) fixed some `-Wextra-semi-stmt warnings`.
258. [Giovanni Cerretani](https://github.com/gcerretani) fixed `-Wunused` warnings on `JSON_DIAGNOSTICS`.
259. [Bogdan Popescu](https://github.com/Kapeli) hosts the [docset](https://github.com/Kapeli/Dash-User-Contributions/tree/master/docsets/JSON_for_Modern_C%2B%2B) for offline documentation viewers.
260. [Carl Smedstad](https://github.com/carlsmedstad) fixed an assertion error when using `JSON_DIAGNOSTICS`.
261. [miikka75](https://github.com/miikka75) provided an important fix to compile C++17 code with Clang 9.
262. [Maarten Becker](https://github.com/kernie) fixed a warning for shadowed variables.
263. [Cristi Vîjdea](https://github.com/axnsan12) fixed typos in the `operator[]` documentation.
264. [Alex Beregszaszi](https://github.com/axic) fixed spelling mistakes in comments.
265. [Dirk Stolle](https://github.com/striezel) fixed typos in documentation.
266. [Daniel Albuschat](https://github.com/daniel-kun) corrected the parameter name in the `parse` documentation.
267. [Prince Mendiratta](https://github.com/Prince-Mendiratta) fixed a link to the FAQ.
268. [Florian Albrechtskirchinger](https://github.com/falbrechtskirchinger) implemented `std::string_view` support for object keys and made dozens of other improvements.
269. [Qianqian Fang](https://github.com/fangq) implemented the Binary JData (BJData) format.
270. [pketelsen](https://github.com/pketelsen) added macros `NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT` and `NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT`.
271. [DarkZeros](https://github.com/DarkZeros) adjusted to code to not clash with Arduino defines.
272. [flagarde](https://github.com/flagarde) fixed the output of `meta()` for MSVC.
273. [Giovanni Cerretani](https://github.com/gcerretani) fixed a check for `std::filesystem`.
274. [Dimitris Apostolou](https://github.com/rex4539) fixed a typo.
275. [Ferry Huberts](https://github.com/fhuberts) fixed a typo.
276. [Michael Nosthoff](https://github.com/heinemml) fixed a typo.
277. [JungHoon Lee](https://github.com/jhnlee) fixed a typo.
278. [Faruk D.](https://github.com/fdiblen) fixed the CITATION.CFF file.
279. [Andrea Cocito](https://github.com/puffetto) added a clarification on macro usage to the documentation.
280. [Krzysiek Karbowiak](https://github.com/kkarbowiak) refactored the tests to use `CHECK_THROWS_WITH_AS`.
281. [Chaoqi Zhang](https://github.com/prncoprs) fixed a typo.
282. [ivanovmp](https://github.com/ivanovmp) fixed a whitespace error.
283. [KsaNL](https://github.com/KsaNL) fixed a build error when including `<windows.h>`.
284. [Andrea Pappacoda](https://github.com/Tachi107) moved `.pc` and `.cmake` files to `share` directory.
285. [Wolf Vollprecht](https://github.com/wolfv) added the `patch_inplace` function.
286. [Jake Zimmerman](https://github.com/jez) highlighted common usage patterns in the README file.
287. [NN](https://github.com/NN---) added the Visual Studio output directory to `.gitignore`.
288. [Romain Reignier](https://github.com/romainreignier) improved the performance of the vector output adapter.
289. [Mike](https://github.com/Mike-Leo-Smith) fixed the `std::iterator_traits`.
290. [Richard Hozák](https://github.com/zxey) added macro `JSON_NO_ENUM` to disable default enum conversions.
291. [vakokako](https://github.com/vakokako) fixed tests when compiling with C++20.
292. [Alexander “weej” Jones](https://github.com/alexweej) fixed an example in the README.
293. [Eli Schwartz](https://github.com/eli-schwartz) added more files to the `include.zip` archive.
294. [Kevin Lu](https://github.com/kevinlul) fixed a compilation issue when typedefs with certain names were present.
295. [Trevor Hickey](https://github.com/luxe) improved the description of an example.
296. [Jef LeCompte](https://github.com/jef) updated the year in the README file.
297. [Alexandre Hamez](https://github.com/ahamez) fixed a warning.
298. [Maninderpal Badhan](https://github.com/mbadhan) fixed a typo.
299. [kevin--](https://github.com/kevin--) added a note to an example in the README file.
300. [I](https://github.com/wx257osn2) fixed a typo.
301. [Gregorio Litenstein](https://github.com/Lord-Kamina) fixed the Clang detection.
302. [Andreas Smas](https://github.com/andoma) added a Doozer badge.
303. [WanCW](https://github.com/wancw) fixed the string conversion with Clang.
304. [zhaohuaxishi](https://github.com/zhaohuaxishi) fixed a Doxygen error.
305. [emvivre](https://github.com/emvivre) removed an invalid parameter from CMake.
306. [Tobias Hermann](https://github.com/Dobiasd) fixed a link in the README file.
307. [Michael](https://github.com/traits) fixed a warning.
308. [Ryan Mulder](https://github.com/ryanjmulder) added `ensure_ascii` to the `dump` function.
309. [Muri Nicanor](https://github.com/murinicanor) fixed the `sed` discovery in the Makefile.
310. [David Avedissian](https://github.com/dgavedissian) implemented SFINAE-friendly `iterator_traits`.
311. [AQNOUCH Mohammed](https://github.com/aqnouch) fixed a typo in the README.
312. [Gareth Sylvester-Bradley](https://github.com/garethsb) added `operator/=` and `operator/` to construct JSON pointers.
313. [Michael Macnair](https://github.com/mykter) added support for afl-fuzz testing.
314. [Berkus Decker](https://github.com/berkus) fixed a typo in the README.
315. [Illia Polishchuk](https://github.com/effolkronium) improved the CMake testing.
316. [Ikko Ashimine](https://github.com/eltociear) fixed a typo.
317. [Raphael Grimm](https://github.com/barcode) added the possibility to define a custom base class.
318. [tocic](https://github.com/tocic) fixed typos in the documentation.
319. [Vertexwahn](https://github.com/Vertexwahn) added Bazel build support.
320. [Dirk Stolle](https://github.com/striezel) fixed typos in the documentation.
321. [DavidKorczynski](https://github.com/DavidKorczynski) added a CIFuzz CI GitHub action.
322. [Finkman](https://github.com/Finkman) fixed the debug pretty-printer.
323. [Florian Segginger](https://github.com/floriansegginger) bumped the years in the README.
324. [haadfida](https://github.com/haadfida) cleaned up the badges of used services.
325. [Arsen Arsenović](https://github.com/ArsenArsen) fixed a build error.
326. [theevilone45](https://github.com/theevilone45) fixed a typo in a CMake file.
327. [Sergei Trofimovich](https://github.com/trofi) fixed the custom allocator support.
328. [Joyce](https://github.com/joycebrum) fixed some security issues in the GitHub workflows.
329. [Nicolas Jakob](https://github.com/njakob) add vcpkg version badge.
330. [Tomerkm](https://github.com/Tomerkm) added tests.
331. [No.](https://github.com/tusooa) fixed the use of `get<>` calls.
332. [taro](https://github.com/tarolling) fixed a typo in the `CODEOWNERS` file.
333. [Ikko Eltociear Ashimine](https://github.com/eltociear) fixed a typo.
334. [Felix Yan](https://github.com/felixonmars) fixed a typo in the README.
335. [HO-COOH](https://github.com/HO-COOH) fixed a parenthesis in the documentation.
336. [Ivor Wanders](https://github.com/iwanders) fixed the examples to catch exception by `const&`.
337. [miny1233](https://github.com/miny1233) fixed a parenthesis in the documentation.
338. [tomalakgeretkal](https://github.com/tomalakgeretkal) fixed a compilation error.
339. [alferov](https://github.com/ALF-ONE) fixed a compilation error.
340. [Craig Scott](https://github.com/craigscott-crascit) fixed a deprecation warning in CMake.
341. [Vyacheslav Zhdanovskiy](https://github.com/ZeronSix) added macros for serialization-only types.
342. [Mathieu Westphal](https://github.com/mwestphal) fixed typos.
343. [scribam](https://github.com/scribam) fixed the MinGW workflow.
344. [Aleksei Sapitskii](https://github.com/aleksproger) added support for Apple's Swift Package Manager.
345. [Benjamin Buch](https://github.com/bebuch) fixed the installation path in CMake.
346. [Colby Haskell](https://github.com/colbychaskell) clarified the parse error message in case a file cannot be opened.
347. [Juan Carlos Arevalo Baeza](https://github.com/TheJCAB) fixed the enum conversion.
348. [alferov](https://github.com/ALF-ONE) fixed a version in the documentation.
349. [ss](https://github.com/serge-s) fixed the amalgamation call.
350. [AniketDhemare](https://github.com/AniketDhemare) fixed a version in the documentation.
351. [Philip Müller](https://github.com/philip-paul-mueller) fixed an example.
352. [Leila Shcheglova](https://github.com/LeilaShcheglova) fixed a warning in a test.
353. [Alex Prabhat Bara](https://github.com/alexprabhat99) fixed a function name in the documentation.
354. [laterlaugh](https://github.com/laterlaugh) fixed some typos.
355. [Yuanhao Jia](https://github.com/MrJia1997) fixed the GDB pretty printer.
356. [Fallen_Breath](https://github.com/Fallen-Breath) fixed an example for JSON Pointer.
357. [Nikhil Idiculla](https://github.com/tsnl) fixed some typos.
358. [Griffin Myers](https://github.com/gmyers18) updated the Natvis file.
359. [thetimr](https://github.com/thetimr) fixed a typo in the documentation.
360. [Balazs Erseki](https://github.com/zerocukor287) fixed a URL in the contribution guidelines.
361. [Niccolò Iardella](https://github.com/rotolof) added `NLOHMANN_DEFINE_DERIVED_TYPE_*` macros.
362. [Borislav Stanimirov](https://github.com/iboB) allowed overriding the CMake target name.
363. [Captain Crutches](https://github.com/captaincrutches) made `iterator_proxy_value` a `std::forward_iterator`.
364. [Fredrik Sandhei](https://github.com/fsandhei) added type conversion support for `std::optional`.
365. [jh96](https://github.com/jordan-hoang) added exceptions when `nullptr` is passed to `parse`.
366. [Stuart Gorman](https://github.com/StuartGorman) fixed number parsing when `EINTR` set in `errno`.
367. [Dylan Baker](https://github.com/dcbaker) generated a pkg-config file that follows the pkg-config conventions.
368. [Tianyi Chen](https://github.com/TianyiChen) optimized the binary `get_number` implementation.
369. [peng-wang-cn](https://github.com/peng-wang-cn) added type conversion support for multidimensional arrays.
370. [Einars Netlis-Galejs](https://github.com/EinarsNG) added `ONLY_SERIALIZE` for `NLOHMANN_DEFINE_DERIVED_TYPE_*` macros.
371. [Marcel](https://github.com/mering) removed `alwayslink=True` Bazel flag.
372. [Harinath Nampally](https://github.com/hnampally) added diagnostic positions to exceptions.
373. [Nissim Armand Ben Danan](https://github.com/NissimBendanan) fixed `NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT` with an empty JSON instance.
374. [Michael Valladolid](https://github.com/codenut) added support for BSON uint64 serialization/deserialization.
375. [Nikhil](https://github.com/nikhilreddydev) updated the documentation.
376. [Nebojša Cvetković](https://github.com/nebkat) added support for BJDATA optimized binary array type.
377. [Sushrut Shringarputale](https://github.com/sushshring) added support for diagnostic positions. 
378. [kimci86](https://github.com/kimci86) templated to `NLOHMANN_DEFINE_TYPE` macros to also support `ordered_json`.
379. [Richard Topchii](https://github.com/richardtop) added support for VisionOS in the Swift Package Manager.
380. [Robert Chisholm](https://github.com/Robadob) fixed a typo.
381. [zjyhjqs](https://github.com/zjyhjqs) added CPack support.
382. [bitFiedler](https://github.com/bitFiedler) made GDB pretty printer work with Python 3.8.
383. [Gianfranco Costamagna](https://github.com/LocutusOfBorg) fixed a compiler warning.
384. [risa2000](https://github.com/risa2000) made `std::filesystem::path` conversion to/from UTF-8 encoded string explicit.

Thanks a lot for helping out! Please [let me know](mailto:mail@nlohmann.me) if I forgot someone.

## Used third-party tools

The library itself consists of a single header file licensed under the MIT license. However, it is built, tested, documented, and whatnot using a lot of third-party tools and services. Thanks a lot!

- [**amalgamate.py - Amalgamate C source and header files**](https://github.com/edlund/amalgamate) to create a single header file
- [**American fuzzy lop**](https://lcamtuf.coredump.cx/afl/) for fuzz testing
- [**AppVeyor**](https://www.appveyor.com) for [continuous integration](https://ci.appveyor.com/project/nlohmann/json) on Windows
- [**Artistic Style**](https://astyle.sourceforge.net) for automatic source code indentation
- [**Clang**](https://clang.llvm.org) for compilation with code sanitizers
- [**CMake**](https://cmake.org) for build automation
- [**Codacy**](https://www.codacy.com) for further [code analysis](https://app.codacy.com/gh/nlohmann/json/dashboard)
- [**Coveralls**](https://coveralls.io) to measure [code coverage](https://coveralls.io/github/nlohmann/json)
- [**Coverity Scan**](https://scan.coverity.com) for [static analysis](https://scan.coverity.com/projects/nlohmann-json)
- [**cppcheck**](https://cppcheck.sourceforge.io) for static analysis
- [**doctest**](https://github.com/onqtam/doctest) for the unit tests
- [**GitHub Changelog Generator**](https://github.com/skywinder/github-changelog-generator) to generate the [ChangeLog](https://github.com/nlohmann/json/blob/develop/ChangeLog.md)
- [**Google Benchmark**](https://github.com/google/benchmark) to implement the benchmarks
- [**Hedley**](https://nemequ.github.io/hedley/) to avoid re-inventing several compiler-agnostic feature macros
- [**lcov**](https://github.com/linux-test-project/lcov) to process coverage information and create an HTML view
- [**libFuzzer**](https://llvm.org/docs/LibFuzzer.html) to implement fuzz testing for OSS-Fuzz
- [**Material for MkDocs**](https://squidfunk.github.io/mkdocs-material/) for the style of the documentation site
- [**MkDocs**](https://www.mkdocs.org) for the documentation site
- [**OSS-Fuzz**](https://github.com/google/oss-fuzz) for continuous fuzz testing of the library ([project repository](https://github.com/google/oss-fuzz/tree/master/projects/json))
- [**Probot**](https://probot.github.io) for automating maintainer tasks such as closing stale issues, requesting missing information, or detecting toxic comments.
- [**Valgrind**](https://valgrind.org) to check for correct memory management

## Notes

### Standards compliance

The library targets strict conformance with [RFC 8259](https://tools.ietf.org/html/rfc8259.html). Both the original [JSONTestSuite](https://github.com/nst/JSONTestSuite) and its updated revision are exercised in CI; their test data is downloaded from [`nlohmann/json_test_data`](https://github.com/nlohmann/json_test_data) at configure time rather than committed to this repository (see [`tests/src/unit-testsuites.cpp`](https://github.com/nlohmann/json/blob/develop/tests/src/unit-testsuites.cpp)):

- The updated revision runs all mandatory `y_` (must-accept) and `n_` (must-reject) cases through the strict [`parse()`](https://json.nlohmann.me/api/basic_json/parse/) entry point; the original suite runs its `n_` cases through `parse()` and its `y_` cases through [`operator>>`](https://json.nlohmann.me/api/operator_gtgt/).
- The `i_` (implementation-defined) cases are, by RFC 8259, free to be accepted *or* rejected, so "passing all `i_` cases" is not a meaningful conformance metric. The library makes deliberate, documented choices there: nesting depth is not artificially limited, a leading UTF-8 byte order mark is silently ignored, [Unicode noncharacters](https://www.unicode.org/faq/private_use.html#nonchar1) are forwarded unchanged, invalid UTF-8 and lone/unpaired UTF-16 surrogates are rejected (stricter than required), and a number that cannot be stored without becoming `NaN`/`INF` raises [`out_of_range.406`](https://json.nlohmann.me/home/exceptions/#jsonexceptionout_of_range406).

One behavioral nuance is worth calling out, because a superficial test often misreads it as non-compliance: [`parse()`](https://json.nlohmann.me/api/basic_json/parse/) is strict and rejects trailing data after a value, whereas [`operator>>`](https://json.nlohmann.me/api/operator_gtgt/) follows relaxed iostream semantics — it parses a single value and leaves the stream positioned right after it. Feeding "a valid document followed by trailing bytes" through `operator>>` reports success; the same input through `parse()` is rejected. This is a documented two-API design, not a conformance gap. See [**parsing**](https://json.nlohmann.me/features/parsing/) for details.

### Character encoding

The library supports **Unicode input** as follows:

- Only **UTF-8** encoded input is supported, which is the default encoding for JSON according to [RFC 8259](https://tools.ietf.org/html/rfc8259.html#section-8.1).
- `std::u16string` and `std::u32string` can be parsed, assuming UTF-16 and UTF-32 encoding, respectively. These encodings are not supported when reading from files or other input containers.
- Other encodings such as Latin-1 or ISO 8859-1 are **not** supported and will yield parse or serialization errors.
- [Unicode noncharacters](https://www.unicode.org/faq/private_use.html#nonchar1) will not be replaced by the library.
- Invalid surrogates (e.g., incomplete pairs such as `\uDEAD`) will yield parse errors.
- The strings stored in the library are UTF-8 encoded. When using the default string type (`std::string`), note that its length/size functions return the number of stored bytes rather than the number of characters or glyphs.
- When you store strings with different encodings in the library, calling [`dump()`](https://json.nlohmann.me/api/basic_json/dump/) may throw an exception unless `json::error_handler_t::replace` or `json::error_handler_t::ignore` are used as error handlers.
- To store wide strings (e.g., `std::wstring`), you need to convert them to a UTF-8 encoded `std::string` before, see [an example](https://json.nlohmann.me/home/faq/#wide-string-handling).

### Comments in JSON

This library does not support comments by default. It does so for three reasons:

1. Comments are not part of the [JSON specification](https://tools.ietf.org/html/rfc8259). You may argue that `//` or `/* */` are allowed in JavaScript, but JSON is not JavaScript.
2. This was not an oversight: Douglas Crockford [wrote on this](https://news.ycombinator.com/item?id=3912149) in May 2012:
  
    > I removed comments from JSON because I saw people were using them to hold parsing directives, a practice which would have destroyed interoperability.  I know that the lack of comments makes some people sad, but it shouldn't.
    >
    > Suppose you are using JSON to keep configuration files, which you would like to annotate. Go ahead and insert all the comments you like. Then pipe it through JSMin before handing it to your JSON parser.
  
3. It is dangerous for interoperability if some libraries would add comment support while others don't. Please check [The Harmful Consequences of the Robustness Principle](https://tools.ietf.org/html/draft-iab-protocol-maintenance-01) on this.

However, you can set parameter `ignore_comments` to true in the `parse` function to ignore `//` or `/* */` comments. Comments will then be treated as whitespace.

### Trailing commas

The JSON specification does not allow trailing commas in arrays and objects, and hence this library is treating them as parsing errors by default.

Like comments, you can set parameter `ignore_trailing_commas` to true in the `parse` function to ignore trailing commas in arrays and objects. Note that a single comma as the only content of the array or object (`[,]` or `{,}`) is not allowed, and multiple trailing commas (`[1,,]`) are not allowed either.

This library does not add trailing commas when serializing JSON data.

For more information, see [JSON With Commas and Comments (JWCC)](https://nigeltao.github.io/blog/2021/json-with-commas-comments.html).

### Order of object keys

By default, the library does not preserve the **insertion order of object elements**. This is standards-compliant, as the [JSON standard](https://tools.ietf.org/html/rfc8259.html) defines objects as "an unordered collection of zero or more name/value pairs".

If you do want to preserve the insertion order, you can try the type [`nlohmann::ordered_json`](https://github.com/nlohmann/json/issues/2179). Alternatively, you can use a more sophisticated ordered map like [`tsl::ordered_map`](https://github.com/Tessil/ordered-map) ([integration](https://github.com/nlohmann/json/issues/546#issuecomment-304447518)) or [`nlohmann::fifo_map`](https://github.com/nlohmann/fifo_map) ([integration](https://github.com/nlohmann/json/issues/485#issuecomment-333652309)).

See the [**documentation on object order**](https://json.nlohmann.me/features/object_order/) for more information.

### Memory Release

We checked with Valgrind and the Address Sanitizer (ASAN) that there are no memory leaks.

If you find that a parsing program with this library does not release memory, please consider the following case, and it may be unrelated to this library.

**Your program is compiled with glibc.** There is a tunable threshold that glibc uses to decide whether to actually return memory to the system or whether to cache it for later reuse. If in your program you make lots of small allocations and those small allocations are not a contiguous block and are presumably below the threshold, then they will not get returned to the OS.
Here is a related issue [#1924](https://github.com/nlohmann/json/issues/1924).

### Further notes

- The code contains numerous debug **assertions** which can be switched off by defining the preprocessor macro `NDEBUG`, see the [documentation of `assert`](https://en.cppreference.com/w/cpp/error/assert). In particular, note [`operator[]`](https://json.nlohmann.me/api/basic_json/operator%5B%5D/) implements **unchecked access** for const objects: If the given key is not present, the behavior is undefined (think of a dereferenced null pointer) and yields an [assertion failure](https://github.com/nlohmann/json/issues/289) if assertions are switched on. If you are not sure whether an element in an object exists, use checked access with the [`at()` function](https://json.nlohmann.me/api/basic_json/at/). Furthermore, you can define `JSON_ASSERT(x)` to replace calls to `assert(x)`. See the [**documentation on runtime assertions**](https://json.nlohmann.me/features/assertions/) for more information.
- As the exact number type is not defined in the [JSON specification](https://tools.ietf.org/html/rfc8259.html), this library tries to choose the best fitting C++ number type automatically. As a result, the type `double` may be used to store numbers which may yield [**floating-point exceptions**](https://github.com/nlohmann/json/issues/181) in certain rare situations if floating-point exceptions have been unmasked in the calling code. These exceptions are not caused by the library and need to be fixed in the calling code, such as by re-masking the exceptions prior to calling library functions.
- The code can be compiled without C++ **runtime type identification** features; that is, you can use the `-fno-rtti` compiler flag.
- **Exceptions** are used widely within the library. They can, however, be switched off with either using the compiler flag `-fno-exceptions` or by defining the symbol `JSON_NOEXCEPTION`. In this case, exceptions are replaced by `abort()` calls. You can further control this behavior by defining `JSON_THROW_USER` (overriding `throw`), `JSON_TRY_USER` (overriding `try`), and `JSON_CATCH_USER` (overriding `catch`). Note that `JSON_THROW_USER` should leave the current scope (e.g., by throwing or aborting), as continuing after it may yield undefined behavior. Note the explanatory [`what()`](https://en.cppreference.com/w/cpp/error/exception/what) string of exceptions is not available for MSVC if exceptions are disabled, see [#2824](https://github.com/nlohmann/json/discussions/2824). See the [**documentation of exceptions**](https://json.nlohmann.me/home/exceptions/) for more information.

## Execute unit tests

To compile and run the tests, you need to execute

```shell
mkdir build
cd build
cmake .. -DJSON_BuildTests=On
cmake --build .
ctest --output-on-failure
```

Note that during the `ctest` stage, several JSON test files are downloaded from an [external repository](https://github.com/nlohmann/json_test_data). If policies forbid downloading artifacts during testing, you can download the files yourself and pass the directory with the test files via `-DJSON_TestDataDirectory=path` to CMake. Then, no Internet connectivity is required. See [issue #2189](https://github.com/nlohmann/json/issues/2189) for more information.

If the testdata is not found, several test suites will fail like this:

```
===============================================================================
json/tests/src/make_test_data_available.hpp:21:
TEST CASE:  check test suite is downloaded

json/tests/src/make_test_data_available.hpp:23: FATAL ERROR: REQUIRE( utils::check_testsuite_downloaded() ) is NOT correct!
  values: REQUIRE( false )
  logged: Test data not found in 'json/cmake-build-debug/json_test_data'.
          Please execute target 'download_test_data' before running this test suite.
          See <https://github.com/nlohmann/json#execute-unit-tests> for more information.

===============================================================================
```

In case you have downloaded the library rather than checked out the code via Git, test `cmake_fetch_content_configure` will fail. Please execute `ctest -LE git_required` to skip these tests. See [issue #2189](https://github.com/nlohmann/json/issues/2189) for more information.

Some tests are requiring network to be properly execute. They are labeled as `git_required`. Please execute `ctest -LE git_required` to skip these tests. See [issue #4851](https://github.com/nlohmann/json/issues/4851) for more information.

Some tests change the installed files and hence make the whole process not reproducible. Please execute `ctest -LE not_reproducible` to skip these tests. See [issue #2324](https://github.com/nlohmann/json/issues/2324) for more information. Furthermore, assertions must be switched off to ensure reproducible builds (see [discussion 4494](https://github.com/nlohmann/json/discussions/4494)).

Note you need to call `cmake -LE "not_reproducible|git_required"` to exclude both labels. See [issue #2596](https://github.com/nlohmann/json/issues/2596) for more information.

As Intel compilers use unsafe floating point optimization by default, the unit tests may fail. Use flag [`/fp:precise`](https://www.intel.com/content/www/us/en/docs/cpp-compiler/developer-guide-reference/2021-8/fp-model-fp.html) then.

---

## File: docs/docset/README.md

# docset

The folder contains the required files to create a [docset](https://kapeli.com/docsets) which can be used in
documentation browsers like [Dash](https://kapeli.com/dash), [Velocity](https://velocity.silverlakesoftware.com), or
[Zeal](https://zealdocs.org).

The docset can be created with

```sh
make nlohmann_json.docset
```

The generated folder `nlohmann_json.docset` can then be opened in the documentation browser.

A recent version is also part of the [Dash user contributions](https://github.com/Kapeli/Dash-User-Contributions/tree/master/docsets/JSON_for_Modern_C%2B%2B).

## Licenses

The [JSON logo](https://commons.wikimedia.org/wiki/File:JSON_vector_logo.svg) is public domain.

---

## File: docs/mkdocs/includes/glossary.md

*[ADL]: Argument-dependent lookup
*[API]: Application Programming Interfaces
*[ASCII]: American Standard Code for Information Interchange
*[BDFL]: Benevolent Dictator for Life
*[BJData]: Binary JData
*[BSON]: Binary JSON
*[CBOR]: Concise Binary Object Representation
*[CC0]: Creative Commons Zero
*[CI]: Continuous Integration
*[DOM]: Document Object Model
*[EOF]: End of File
*[FAQ]: Frequently Asked Questions
*[GCC]: GNU Compiler Collection
*[HTTP]: Hypertext Transfer Protocol
*[ICC]: Intel C++ Compiler
*[IEEE]: Institute of Electrical and Electronics Engineers
*[ISO]: International Organization for Standardization
*[JSON]: JavaScript Object Notation
*[MIT]: Massachusetts Institute of Technology
*[MSVC]: Microsoft Visual C++
*[MsgPack]: MessagePack
*[NASA]: National Aeronautics and Space Administration
*[NDK]: Native Development Kit
*[NaN]: Not a Number
*[RFC]: Request for Comments
*[RTTI]: Runtime Type Information
*[SAX]: Simple API for XML
*[SDK]: Software Development Kit
*[SFINAE]: Substitution failure is not an error
*[SHA]: Secure Hash Algorithm
*[SPDX]: Software Package Data Exchange
*[STL]: Standard Template Library
*[UBJSON]: Universal Binary JSON
*[UTF]: Unicode Transformation Format

---

## File: docs/mkdocs/docs/home/architecture.md

# Architecture

!!! info

    This page is still under construction. Its goal is to provide a high-level overview of the library's architecture.
    This should help new contributors to get an idea of the used concepts and where to make changes.

## Overview

The main structure is class [nlohmann::basic_json](../api/basic_json/index.md).

- public API
- container interface
- iterators

## Template specializations

- describe template parameters of `basic_json`
- [`json`](../api/json.md)
- [`ordered_json`](../api/ordered_json.md) via [`ordered_map`](../api/ordered_map.md)

## Value storage

Values are stored as a tagged union of [value_t](../api/basic_json/value_t.md) and json_value.

```cpp
/// the type of the current element
value_t m_type = value_t::null;

/// the value of the current element
json_value m_value = {};
```

with

```cpp
enum class value_t : std::uint8_t
{
    null,             ///< null value
    object,           ///< object (unordered set of name/value pairs)
    array,            ///< array (ordered collection of values)
    string,           ///< string value
    boolean,          ///< boolean value
    number_integer,   ///< number value (signed integer)
    number_unsigned,  ///< number value (unsigned integer)
    number_float,     ///< number value (floating-point)
    binary,           ///< binary array (ordered collection of bytes)
    discarded         ///< discarded by the parser callback function
};

union json_value {
  /// object (stored with pointer to save storage)
  object_t *object;
  /// array (stored with pointer to save storage)
  array_t *array;
  /// string (stored with pointer to save storage)
  string_t *string;
  /// binary (stored with pointer to save storage)
  binary_t *binary;
  /// boolean
  boolean_t boolean;
  /// number (integer)
  number_integer_t number_integer;
  /// number (unsigned integer)
  number_unsigned_t number_unsigned;
  /// number (floating-point)
  number_float_t number_float;
};
```

## Parsing inputs (deserialization)

Input is read via **input adapters** that abstract a source with a common interface:

```cpp
/// read a single character
std::char_traits<char>::int_type get_character() noexcept;

/// read multiple characters to a destination buffer and
/// returns the number of characters successfully read
template<class T>
std::size_t get_elements(T* dest, std::size_t count = 1);
```

List examples of input adapters.

## SAX Interface

TODO

## Writing outputs (serialization)

Output is written via **output adapters**:

```cpp
template<typename T>
void write_character(CharType c);

template<typename CharType>
void write_characters(const CharType* s, std::size_t length);
```

List examples of output adapters.

## Value conversion

```cpp
template<class T>
void to_json(basic_json& j, const T& t);

template<class T>
void from_json(const basic_json& j, T& t);
```

## Additional features

- JSON Pointers
- Binary formats
- Custom base class
- Conversion macros

## Details namespace

- C++ feature backports

---

## File: docs/mkdocs/docs/home/customers.md

# Customers

The library is used in multiple projects, applications, operating systems, etc. The list below is not exhaustive, but
the result of an internet search. If you know further customers of the library, [please let me know](mailto:mail@nlohmann.me).

[](../images/customers.png)

## Space Exploration

- [**Peregrine Lunar Lander Flight 01**](https://en.wikipedia.org/wiki/Peregrine_Mission_One) - The library was used for payload management in the **Peregrine Moon Lander**, developed by **Astrobotic Technology** and launched as part of NASA's **Commercial Lunar Payload Services (CLPS)** program. After six days in orbit, the spacecraft was intentionally redirected into Earth's atmosphere, where it burned up over the Pacific Ocean on **January 18, 2024**.

## Automotive

- [**Alexa Auto SDK**](https://github.com/alexa/alexa-auto-sdk), a software development kit enabling the integration of Alexa into automotive systems
- [**Apollo**](https://github.com/ApolloAuto/apollo), a framework for building autonomous driving systems
- [**Automotive Grade Linux (AGL)**](https://download.automotivelinux.org/AGL/release/jellyfish/latest/qemux86-64/deploy/licenses/nlohmann-json/), a collaborative open-source platform for automotive software development
- [**Genesis Motor** (infotainment)](http://webmanual.genesis.com/ccIC/AVNT/JW/KOR/English/reference010.html), a luxury automotive brand
- [**Hyundai** (infotainment)](https://www.hyundai.com/wsvc/ww/download.file.do?id=/content/hyundai/ww/data/opensource/data/GN7-2022/licenseCode/info), a global automotive brand
- [**Kia** (infotainment)](http://webmanual.kia.com/PREM_GEN6/AVNT/RJPE/KOR/Korean/reference010.html), a global automotive brand
- [**Mercedes-Benz Operating System (MB.OS)**](https://group.mercedes-benz.com/careers/about-us/mercedes-benz-operating-system/), a core component of the vehicle software ecosystem from Mercedes-Benz
- [**Rivian** (infotainment)](https://assets.ctfassets.net/2md5qhoeajym/3cwyo4eoufk4yingUwusFt/ded2c47da620fdfc99c88c7156d2c1d8/In-Vehicle_OSS_Attribution_2024__11-24_.pdf), an electric vehicle manufacturer
- [**Suzuki** (infotainment)](https://www.globalsuzuki.com/motorcycle/ipc/oss/oss_48KA_00.pdf), a global automotive and motorcycle manufacturer

## Gaming and Entertainment

- [**Assassin's Creed: Mirage**](https://www.mobygames.com/person/1195889/niels-lohmann/credits/), a stealth-action game set in the Middle East, focusing on the journey of a young assassin with classic parkour and stealth mechanics
- [**Chasm: The Rift**](https://www.mobygames.com/person/1195889/niels-lohmann/credits/), a first-person shooter blending horror and adventure, where players navigate dark realms and battle monsters
- [**College Football 25**](https://www.mobygames.com/person/1195889/niels-lohmann/credits/), a college football simulation game featuring gameplay that mimics real-life college teams and competitions
- [**Concepts**](https://concepts.app/en/licenses), a digital sketching app designed for creative professionals, offering flexible drawing tools for illustration, design, and brainstorming
- [**Depthkit**](https://www.depthkit.tv/third-party-licenses), a tool for creating and capturing volumetric video, enabling immersive 3D experiences and interactive content
- [**IMG.LY**](https://img.ly/acknowledgements), a platform offering creative tools and SDKs for integrating advanced image and video editing in applications
- [**LOOT**](https://loot.readthedocs.io/_/downloads/en/0.13.0/pdf/), a tool for optimizing the load order of game plugins, commonly used in The Elder Scrolls and Fallout series
- [**Madden NFL 25**](https://www.mobygames.com/person/1195889/niels-lohmann/credits/), a sports simulation game capturing the excitement of American football with realistic gameplay and team management features
- [**Marne**](https://marne.io/licenses), an unofficial private server platform for hosting custom Battlefield 1 game experiences
- [**Minecraft**](https://www.minecraft.net/zh-hant/attribution), a popular sandbox video game
- [**NHL 22**](https://www.mobygames.com/person/1195889/niels-lohmann/credits/), a hockey simulation game offering realistic gameplay, team management, and various modes to enhance the hockey experience
- [**Pixelpart**](https://pixelpart.net/documentation/book/third-party.html), a 2D animation and video compositing software that allows users to create animated graphics and visual effects with a focus on simplicity and ease of use
- [**Razer Cortex**](https://mysupport.razer.com/app/answers/detail/a_id/14146/~/open-source-software-for-razer-software), a gaming performance optimizer and system booster designed to enhance the gaming experience
- [**Red Dead Redemption II**](https://www.mobygames.com/person/1195889/niels-lohmann/credits/), an open-world action-adventure game following an outlaw's story in the late 1800s, emphasizing deep storytelling and immersive gameplay
- [**Snapchat**](https://www.snap.com/terms/license-android), a multimedia messaging and augmented reality app for communication and entertainment
- [**Tactics Ogre: Reborn**](https://www.square-enix-games.com/en_US/documents/tactics-ogre-reborn-pc-installer-software-and-associated-plug-ins-disclosure), a tactical role-playing game featuring strategic battles and deep storytelling elements
- [**Throne and Liberty**](https://www.amazon.com/gp/help/customer/display.html?nodeId=T7fLNw5oAevCMtJFPj&pop-up=1), an MMORPG that offers an expansive fantasy world with dynamic gameplay and immersive storytelling
- [**Unity Vivox**](https://docs.unity3d.com/Packages/com.unity.services.vivox@15.1/license/Third%20Party%20Notices.html), a communication service that enables voice and text chat functionality in multiplayer games developed with Unity
- [**Zool: Redimensioned**](https://www.mobygames.com/person/1195889/niels-lohmann/credits/), a modern reimagining of the classic platformer featuring fast-paced gameplay and vibrant environments
- [**immersivetech**](https://immersitech.io/open-source-third-party-software/), a technology company focused on immersive experiences, providing tools and solutions for virtual and augmented reality applications

## Consumer Electronics

- [**Audinate**](https://www.audinate.com/legal/software-licensing/dante-av-h-open-source-licenses/), a provider of networked audio solutions specializing in Dante technology, which facilitates high-quality digital audio transport over IP networks
- [**Canon CanoScan LIDE**](https://carolburo.com/wp-content/uploads/2024/06/LiDE400_OnlineManual_Win_FR_V02.pdf), a series of flatbed scanners offering high-resolution image scanning for home and office use
- [**Canon PIXMA Printers**](https://www.mediaexpert.pl/products/files/73/7338196/Instrukcja-obslugi-CANON-Pixma-TS7450i.pdf), a line of all-in-one inkjet printers known for high-quality printing and wireless connectivity
- [**Cisco Webex Desk Camera**](https://www.cisco.com/c/dam/en_us/about/doing_business/open_source/docs/CiscoWebexDeskCamera-23-1622100417.pdf), a video camera designed for professional-quality video conferencing and remote collaboration
- [**Philips Hue Personal Wireless Lighting**](http://2ak5ape.257.cz/), a smart lighting system for customizable and wireless home illumination
- [**Ray-Ban Meta Smart glasses**](https://www.meta.com/de/en/legal/smart-glasses/third-party-notices-android/03/), a pair of smart glasses designed for capturing photos and videos with integrated connectivity and social features
- [**Razer Synapse**](https://mysupport.razer.com/app/answers/detail/a_id/14146/~/open-source-software-for-razer-software), a unified configuration software enabling hardware customization for Razer devices
- [**Siemens SINEMA Remote Connect**](https://cache.industry.siemens.com/dl/files/790/109793790/att_1054961/v2/OSS_SINEMA-RC_86.pdf), a remote connectivity solution for monitoring and managing industrial networks and devices securely
- [**Sony PlayStation 4**](https://doc.dl.playstation.net/doc/ps4-oss/index.html), a gaming console developed by Sony that offers a wide range of games and multimedia entertainment features
- [**Sony Virtual Webcam Driver for Remote Camera**](https://helpguide.sony.net/rc/vwd/v1/zh-cn/print.pdf), a software driver that enables the use of Sony cameras as virtual webcams for video conferencing and streaming

## Operating Systems

- [**Apple iOS and macOS**](https://www.apple.com/macos), a family of operating systems developed by Apple, including iOS for mobile devices and macOS for desktop computers
- [**Google Fuchsia**](https://fuchsia.googlesource.com/third_party/json/), an open-source operating system developed by Google, designed to be secure, updatable, and adaptable across various devices
- [**SerenityOS**](https://github.com/SerenityOS/serenity), an open-source operating system that aims to provide a simple and beautiful user experience with a focus on simplicity and elegance
- [**Yocto**](http://ftp.emacinc.com/openembedded-sw/kirkstone-icop-5.15-kirkstone-6.0/archive-2024-10/pn8m-090t-ppc/licenses/nlohmann-json/), a Linux-based build system for creating custom operating systems and software distributions, tailored for embedded devices and IoT applications

## Development Tools and IDEs

- [**Accentize SpectralBalance**](https://www.accentize.com/products/SpectralBalanceManual.pdf), an adaptive speech analysis tool designed to enhance audio quality by optimizing frequency balance in recordings
- [**Arm Compiler for Linux**](https://documentation-service.arm.com/static/66558e9d876c8d213b7843e4), a software development toolchain for compiling and optimizing applications on Arm-based Linux systems
- [**BBEdit**](https://s3.amazonaws.com/BBSW-download/BBEdit_15.1.2_User_Manual.pdf), a professional text and code editor for macOS
- [**CoderPad**](https://coderpad.io), a collaborative coding platform that enables real-time code interviews and assessments for developers; the library is included in every CoderPad instance and can be accessed with a simple `#include "json.hpp"`
- [**Compiler Explorer**](https://godbolt.org), a web-based tool that allows users to write, compile, and visualize the assembly output of code in various programming languages; the library is readily available and accessible with the directive `#include <nlohmann/json.hpp>`.
- [**GitHub CodeQL**](https://github.com/github/codeql), a code analysis tool used for identifying security vulnerabilities and bugs in software through semantic queries
- [**Hex-Rays**](https://docs.hex-rays.com/user-guide/user-interface/licenses), a reverse engineering toolset for analyzing and decompiling binaries, primarily used for security research and vulnerability analysis
- [**ImHex**](https://github.com/WerWolv/ImHex), a hex editor designed for reverse engineering, providing advanced features for data analysis and manipulation
- [**Intel GPA Framework**](https://intel.github.io/gpasdk-doc/src/licenses.html), a suite of cross-platform tools for capturing, analyzing, and optimizing graphics applications across different APIs
- [**Intopix**](https://www.intopix.com/software-licensing), a provider of advanced image processing and compression solutions used in software development and AV workflows
- [**Java SE**](https://www.oracle.com/a/tech/docs/jdk8-lium.pdf), the core Java platform that provides the libraries and runtime needed to build and run general-purpose Java applications
- [**MKVToolNix**](https://mkvtoolnix.download/doc/README.md), a set of tools for creating, editing, and inspecting MKV (Matroska) multimedia container files
- [**Meta Yoga**](https://github.com/facebook/yoga), a layout engine that facilitates flexible and efficient user interface design across multiple platforms
- [**NVIDIA Nsight Compute**](https://docs.nvidia.com/nsight-compute/2022.2/pdf/CopyrightAndLicenses.pdf), a performance analysis tool for CUDA applications that provides detailed insights into GPU performance metrics
- [**Notepad++**](https://github.com/notepad-plus-plus/notepad-plus-plus), a free source code editor that supports various programming languages
- [**OpenRGB**](https://gitlab.com/CalcProgrammer1/OpenRGB), an open source RGB lighting control that doesn't depend on manufacturer software
- [**OpenTelemetry C++**](https://github.com/open-telemetry/opentelemetry-cpp), a library for collecting and exporting observability data in C++, enabling developers to implement distributed tracing and metrics in their application
- [**Qt Creator**](https://doc.qt.io/qtcreator/qtcreator-attribution-json-nlohmann.html), an IDE for developing applications using the Qt application framework
- [**Scanbot SDK**](https://docs.scanbot.io/barcode-scanner-sdk/web/third-party-libraries/), a software development kit (SDK) that provides tools for integrating advanced document scanning and barcode scanning capabilities into applications

## Machine Learning and AI

- [**Apple Core ML Tools**](https://github.com/apple/coremltools), a set of tools for converting and configuring machine learning models for deployment in Apple's Core ML framework
- [**Avular Mobile Robotics**](https://www.avular.com/licenses/nlohmann-json-3.9.1.txt), a platform for developing and deploying mobile robotics solutions
- [**Google gemma.cpp**](https://github.com/google/gemma.cpp), a lightweight C++ inference engine designed for running AI models from the Gemma family
- [**llama.cpp**](https://github.com/ggerganov/llama.cpp), a C++ library designed for efficient inference of large language models (LLMs), enabling streamlined integration into applications
- [**MLX**](https://github.com/ml-explore/mlx), an array framework for machine learning on Apple Silicon
- [**Mozilla llamafile**](https://github.com/Mozilla-Ocho/llamafile), a tool designed for distributing and executing large language models (LLMs) efficiently using a single file format
- [**NVIDIA ACE**](https://docs.nvidia.com/ace/latest/index.html), a suite of real-time AI solutions designed for the development of interactive avatars and digital human applications, enabling scalable and sophisticated user interactions
- [**Peer**](https://support.peer.inc/hc/en-us/articles/17261335054235-Licenses), a platform offering personalized AI assistants for interactive learning and creative collaboration
- [**stable-diffusion.cpp**](https://github.com/leejet/stable-diffusion.cpp), a C++ implementation of the Stable Diffusion image generation model
- [**TanvasTouch**](https://tanvas.co/tanvastouch-sdk-third-party-acknowledgments), a software development kit (SDK) that enables developers to create tactile experiences on touchscreens, allowing users to feel textures and physical sensations in a digital environment
- [**TensorFlow**](https://github.com/tensorflow/tensorflow), a machine learning framework that facilitates the development and training of models, supporting data serialization and efficient data exchange between components

## Scientific Research and Analysis

- [**BLACK**](https://www.black-sat.org/en/stable/installation/linux.html), a bounded linear temporal logic (LTL) satisfiability checker
- [**CERN Atlas Athena**](https://gitlab.cern.ch/atlas/athena/-/blob/main/Control/PerformanceMonitoring/PerfMonComps/src/PerfMonMTSvc.h), a software framework used in the ATLAS experiment at the Large Hadron Collider (LHC) for performance monitoring
- [**ICU**](https://github.com/unicode-org/icu), the International Components for Unicode, a mature library for software globalization and multilingual support
- [**KAMERA**](https://github.com/Kitware/kamera), a platform for synchronized data collection and real-time deep learning to map marine species like polar bears and seals, aiding Arctic ecosystem research
- [**KiCad**](https://gitlab.com/kicad/code/kicad/-/tree/master/thirdparty/nlohmann_json), a free and open-source software suite for electronic design automation
- [**Maple**](https://www.maplesoft.com/support/help/Maple/view.aspx?path=copyright), a symbolic and numeric computing environment for advanced mathematical modeling and analysis
- [**MeVisLab**](https://mevislabdownloads.mevis.de/docs/current/MeVis/ThirdParty/Documentation/Publish/ThirdPartyReference/index.html), a software framework for medical image processing and visualization.
- [**OpenPMD API**](https://openpmd-api.readthedocs.io/en/0.8.0-alpha/backends/json.html), a versatile programming interface for accessing and managing scientific data, designed to facilitate the efficient storage, retrieval, and sharing of simulation data across various applications and platforms
- [**ParaView**](https://github.com/Kitware/ParaView), an open-source tool for large-scale data visualization and analysis across various scientific domains
- [**QGIS**](https://gitlab.b-data.ch/qgis/qgis/-/blob/backport-57658-to-release-3_34/external/nlohmann/json.hpp), a free and open-source geographic information system (GIS) application that allows users to create, edit, visualize, and analyze geospatial data across a variety of formats
- [**VTK**](https://github.com/Kitware/VTK), a software library for 3D computer graphics, image processing, and visualization
- [**VolView**](https://github.com/Kitware/VolView), a lightweight application for interactive visualization and analysis of 3D medical imaging data.

## Business and Productivity Software

- [**ArcGIS PRO**](https://www.esri.com/content/dam/esrisites/en-us/media/legal/open-source-acknowledgements/arcgis-pro-2-8-attribution-report.html), a desktop geographic information system (GIS) application developed by Esri for mapping and spatial analysis
- [**Autodesk Desktop**](https://damassets.autodesk.net/content/dam/autodesk/www/Company/legal-notices-trademarks/autodesk-desktop-platform-components/internal-autodesk-components-web-page-2023.pdf), a software platform developed by Autodesk for creating and managing desktop applications and services
- [**Check Point**](https://www.checkpoint.com/about-us/copyright-and-trademarks/), a cybersecurity company specializing in threat prevention and network security solutions, offering a range of products designed to protect enterprises from cyber threats and ensure data integrity
- [**Microsoft Office for Mac**](https://officecdnmac.microsoft.com/pr/legal/mac/OfficeforMacAttributions.html), a suite of productivity applications developed by Microsoft for macOS, including tools for word processing, spreadsheets, and presentations
- [**Microsoft Teams**](https://www.microsoft.com/microsoft-teams/), a team collaboration application offering workspace chat and video conferencing, file storage, and integration of proprietary and third-party applications and services
- [**Nexthink Infinity**](https://docs.nexthink.com/legal/services-terms/experience-open-source-software-licenses/infinity-2022.8-software-licenses), a digital employee experience management platform for monitoring and improving IT performance
- [**Sophos Connect Client**](https://docs.sophos.com/nsg/licenses/SophosConnect/SophosConnectAttribution.html), a secure VPN client from Sophos that allows remote users to connect to their corporate network, ensuring secure access to resources and data
- [**Stonebranch**](https://stonebranchdocs.atlassian.net/wiki/spaces/UA77/pages/799545647/Licenses+for+Third-Party+Libraries), a cloud-based cybersecurity solution that integrates backup, disaster recovery, and cybersecurity features to protect data and ensure business continuity for organizations
- [**Tablecruncher**](https://tablecruncher.com/), a data analysis tool that allows users to import, analyze, and visualize spreadsheet data, offering interactive features for better insights and decision-making
- [**magicplan**](https://help.magicplan.app/acknowledgments), a mobile application for creating floor plans and interior designs using augmented reality

## Databases and Big Data

- [**ADIOS2**](https://code.ornl.gov/ecpcitest/adios2/-/tree/pr4285_FFSUpstream/thirdparty/nlohmann_json?ref_type=heads), a data management framework designed for high-performance input and output operations
- [**Cribl Stream**](https://docs.cribl.io/stream/third-party-current-list/), a real-time data processing platform that enables organizations to collect, route, and transform observability data, enhancing visibility and insights into their systems
- [**DB Browser for SQLite**](https://github.com/sqlitebrowser/sqlitebrowser), a visual open-source tool for creating, designing, and editing SQLite database files
- [**MySQL Connector/C++**](https://docs.oracle.com/cd/E17952_01/connector-cpp-9.1-license-com-en/license-opentelemetry-cpp-com.html), a C++ library for connecting and interacting with MySQL databases
- [**MySQL NDB Cluster**](https://downloads.mysql.com/docs/licenses/cluster-9.0-com-en.pdf), a distributed database system that provides high availability and scalability for MySQL databases
- [**MySQL Shell**](https://downloads.mysql.com/docs/licenses/mysql-shell-8.0-gpl-en.pdf), an advanced client and code editor for interacting with MySQL servers, supporting SQL, Python, and JavaScript
- [**PrestoDB**](https://github.com/prestodb/presto), a distributed SQL query engine designed for large-scale data analytics, originally developed by Facebook
- [**ROOT Data Analysis Framework**](https://root.cern/doc/v614/classnlohmann_1_1basic__json.html), an open-source data analysis framework widely used in high-energy physics and other fields for data processing and visualization
- [**WiredTiger**](https://github.com/wiredtiger/wiredtiger), a high-performance storage engine for databases, offering support for compression, concurrency, and checkpointing

## Simulation and Modeling

- [**Arcturus HoloSuite**](https://www.datocms-assets.com/104353/1698904597-holosuite-third-party-software-credits-and-attributions-2.pdf), a software toolset for capturing, editing, and streaming volumetric video, featuring advanced compression technologies for high-quality 3D content creation
- [**azul**](https://pure.tudelft.nl/ws/files/85338589/tgis.12673.pdf), a fast and efficient 3D city model viewer designed for visualizing urban environments and spatial data
- [**Blender**](https://projects.blender.org/blender/blender/search?q=nlohmann), a free and open-source 3D creation suite for modeling, animation, rendering, and more
- [**cpplot**](https://cpplot.readthedocs.io/en/latest/library_api/function_eigen_8h_1ac080eac0541014c5892a55e41bf785e6.html), a library for creating interactive graphs and charts in C++, which can be viewed in web browsers
- [**Foundry Nuke**](https://learn.foundry.com/nuke/content/misc/studio_third_party_libraries.html), a powerful node-based digital compositing and visual effects application used in film and television post-production
- [**GAMS**](https://www.gams.com/47/docs/THIRDPARTY.html), a high-performance mathematical modeling system for optimization and decision support
- [**Kitware SMTK**](https://github.com/Kitware/SMTK), a software toolkit for managing simulation models and workflows in scientific and engineering applications
- [**M-Star**](https://docs.mstarcfd.com/3_Licensing/thirdparty-licenses.html), a computational fluid dynamics software for simulating and analyzing fluid flow
- [**MapleSim CAD Toolbox**](https://www.maplesoft.com/support/help/MapleSim/view.aspx?path=CADToolbox/copyright), a software extension for MapleSim that integrates CAD models, allowing users to import, manipulate, and analyze 3D CAD data within the MapleSim environment for enhanced modeling and simulation
- [**NVIDIA Omniverse**](https://docs.omniverse.nvidia.com/composer/latest/common/product-licenses/usd-explorer/usd-explorer-2023.2.0-licenses-manifest.html), a platform for 3D content creation and collaboration that enables real-time simulations and interactive experiences across various industries
- [**Pixar Renderman**](https://rmanwiki-26.pixar.com/space/REN26/19662083/Legal+Notice), a photorealistic 3D rendering software developed by Pixar, widely used in the film industry for creating high-quality visual effects and animations
- [**ROS - Robot Operating System**](http://docs.ros.org/en/noetic/api/behaviortree_cpp/html/json_8hpp_source.html), a set of software libraries and tools that assist in developing robot applications
- [**UBS**](https://www.ubs.com/), a multinational financial services and banking company

## Enterprise and Cloud Applications

- [**Acronis Cyber Protect Cloud**](https://care.acronis.com/s/article/59533-Third-party-software-used-in-Acronis-Cyber-Protect-Cloud?language=en_US), an all-in-one data protection solution that combines backup, disaster recovery, and cybersecurity to safeguard business data from threats like ransomware
- [**Baereos**](https://gitlab.tiger-computing.co.uk/packages/bareos/-/blob/tiger/bullseye/third-party/CLI11/examples/json.cpp), a backup solution that provides data protection and recovery options for various environments, including physical and virtual systems
- [**Bitdefender Home Scanner**](https://www.bitdefender.de/site/Main/view/home-scanner-open-source.html), a tool from Bitdefender that scans devices for malware and security threats, providing a safeguard against potential online dangers
- [**Citrix Provisioning**](https://docs.citrix.com/en-us/provisioning/2203-ltsr/downloads/pvs-third-party-notices-2203.pdf), a solution that streamlines the delivery of virtual desktops and applications by allowing administrators to manage and provision resources efficiently across multiple environments
- [**Citrix Virtual Apps and Desktops**](https://docs.citrix.com/en-us/citrix-virtual-apps-desktops/2305/downloads/third-party-notices-apps-and-desktops.pdf), a solution from Citrix that delivers virtual apps and desktops
- [**Cyberarc**](https://docs.cyberark.com/Downloads/Legal/Privileged%20Session%20Manager%20for%20SSH%20Third-Party%20Notices.pdf), a security solution that specializes in privileged access management, enabling organizations to control and monitor access to critical systems and data, thereby enhancing overall cybersecurity posture
- [**Egnyte Desktop**](https://helpdesk.egnyte.com/hc/en-us/articles/360007071732-Third-Party-Software-Acknowledgements), a secure cloud storage solution designed for businesses, enabling file sharing, collaboration, and data management across teams while ensuring compliance and data protection
- [**Elster**](https://www.secunet.com/en/about-us/press/article/elstersecure-bietet-komfortablen-login-ohne-passwort-dank-secunet-protect4use), a digital platform developed by German tax authorities for secure and efficient electronic tax filing and management using secunet protect4use
- [**Ethereum Solidity**](https://github.com/ethereum/solidity), a high-level, object-oriented programming language designed for implementing smart contracts on the Ethereum platform
- [**Inciga**](https://fossies.org/linux/icinga2/third-party/nlohmann_json/json.hpp), a monitoring tool for IT infrastructure, designed to provide insights into system performance and availability through customizable dashboards and alerts
- [**Intel Accelerator Management Daemon for VMware ESXi**](https://downloadmirror.intel.com/772507/THIRD-PARTY.txt), a management tool designed for monitoring and controlling Intel hardware accelerators within VMware ESXi environments, optimizing performance and resource allocation
- [**Juniper Identity Management Service**](https://www.juniper.net/documentation/us/en/software/jims/jims-guide/jims-guide.pdf)
- [**Microsoft Azure IoT SDK**](https://library.e.abb.com/public/2779c5f85f30484192eb3cb3f666a201/IP%20Gateway%20Open%20License%20Declaration_9AKK108467A4095_Rev_C.pdf), a collection of tools and libraries to help developers connect, build, and deploy Internet of Things (IoT) solutions on the Azure cloud platform
- [**Microsoft WinGet**](https://github.com/microsoft/winget-cli), a command-line utility included in the Windows Package Manager
- [**plexusAV**](https://www.sisme.com/media/10994/manual_plexusav-p-avn-4-form8244-c.pdf), a high-performance AV-over-IP transceiver device capable of video encoding and decoding using the IPMX standard
- [**Pointr**](https://docs-dev.pointr.tech/docs/8.x/Developer%20Portal/Open%20Source%20Licenses/), a platform for indoor positioning and navigation solutions, offering tools and SDKs for developers to create location-based applications
- [**secunet protect4use**](https://www.secunet.com/en/about-us/press/article/elstersecure-bietet-komfortablen-login-ohne-passwort-dank-secunet-protect4use), a secure, passwordless multifactor authentication solution that transforms smartphones into digital keyrings, ensuring high security for online services and digital identities
- [**Sencore MRD 7000**](https://www.foccusdigital.com/wp-content/uploads/2025/03/MRD-7000-Manual-8175V.pdf), a professional multi-channel receiver and decoder supporting UHD and HD stream decoding

---

## File: docs/mkdocs/docs/home/design_goals.md

# Design goals

There are myriads of [JSON](https://json.org) libraries out there, and each may even have its reason to exist. Our class had these design goals:

- **Intuitive syntax**. In languages such as Python, JSON feels like a first-class data type. We used all the operator magic of modern C++ to achieve the same feeling in your code.

- **Trivial integration**. Our whole code consists of a single header file [`json.hpp`](https://github.com/nlohmann/json/blob/develop/single_include/nlohmann/json.hpp). That's it. No library, no subproject, no dependencies, no complex build system. The class is written in vanilla C++11. All in all, everything should require no adjustment of your compiler flags or project settings.

- **Serious testing**. Our class is heavily [unit-tested](https://github.com/nlohmann/json/tree/develop/tests/src) and covers [100%](https://coveralls.io/r/nlohmann/json) of the code, including all exceptional behavior. Furthermore, we checked with [Valgrind](http://valgrind.org) and the [Clang Sanitizers](https://clang.llvm.org/docs/index.html) that there are no memory leaks. [Google OSS-Fuzz](https://github.com/google/oss-fuzz/tree/master/projects/json) additionally runs fuzz tests against all parsers 24/7, effectively executing billions of tests so far. To maintain high quality, the project is following the [Core Infrastructure Initiative (CII) best practices](https://bestpractices.coreinfrastructure.org/projects/289).

Other aspects were not so important to us:

- **Memory efficiency**. Each JSON object has an overhead of one pointer (the maximal size of a union) and one enumeration element (1 byte). The default generalization uses the following C++ data types: `std::string` for strings, `int64_t`, `uint64_t` or `double` for numbers, `std::map` for objects, `std::vector` for arrays, and `bool` for Booleans. However, you can template the generalized class `basic_json` to your needs.

- **Speed**. There are certainly [faster JSON libraries](https://github.com/miloyip/nativejson-benchmark#parsing-time) out there. However, if your goal is to speed up your development by adding JSON support with a single header, then this library is the way to go. If you know how to use a `std::vector` or `std::map`, you are already set.

See the [contribution guidelines](https://github.com/nlohmann/json/blob/master/.github/CONTRIBUTING.md#please-dont) for more information.

---

## File: docs/mkdocs/docs/home/exceptions.md

# Exceptions

## Overview

### Base type

All exceptions inherit from class `json::exception` (which in turn inherits from `std::exception`). It is used as the base class for all exceptions thrown by the `basic_json` class. This class can hence be used as "wildcard" to catch exceptions.

``` mermaid
classDiagram
  direction LR
    class `std::exception` {
        <>
    }

    class `json::exception` {
        +const int id
        +const char* what() const
    }

    class `json::parse_error` {
        +const std::size_t byte
    }

    class `json::invalid_iterator`
    class `json::type_error`
    class `json::out_of_range`
    class `json::other_error`

    `std::exception` <|-- `json::exception`
    `json::exception` <|-- `json::parse_error`
    `json::exception` <|-- `json::invalid_iterator`
    `json::exception` <|-- `json::type_error`
    `json::exception` <|-- `json::out_of_range`
    `json::exception` <|-- `json::other_error`
```

### Switch off exceptions

Exceptions are used widely within the library. They can, however, be switched off with either using the compiler flag `-fno-exceptions` or by defining the symbol [`JSON_NOEXCEPTION`](../api/macros/json_noexception.md). In this case, exceptions are replaced by `abort()` calls. You can further control this behavior by defining `JSON_THROW_USER` (overriding `#!cpp throw`), `JSON_TRY_USER` (overriding `#!cpp try`), and `JSON_CATCH_USER` (overriding `#!cpp catch`).

Note that [`JSON_THROW_USER`](../api/macros/json_throw_user.md) should leave the current scope (e.g., by throwing or aborting), as continuing after it may yield undefined behavior.

??? example

    The code below switches off exceptions and creates a log entry with a detailed error message in case of errors.

    ```cpp
    #include 
    
    #define JSON_TRY_USER if(true)
    #define JSON_CATCH_USER(exception) if(false)
    #define JSON_THROW_USER(exception)                           \
        {std::clog << "Error in " << __FILE__ << ":" << __LINE__ \
                   << " (function " << __FUNCTION__ << ") - "    \
                   << (exception).what() << std::endl;           \
         std::abort();}
    
    #include <nlohmann/json.hpp>
    ```

Note the explanatory [`what()`](https://en.cppreference.com/w/cpp/error/exception/what) string of exceptions is not available for MSVC if exceptions are disabled, see [#2824](https://github.com/nlohmann/json/discussions/2824).

See [documentation of `JSON_TRY_USER`, `JSON_CATCH_USER` and `JSON_THROW_USER`](../api/macros/json_throw_user.md) for more information.

### Extended diagnostic messages

Exceptions in the library are thrown in the local context of the JSON value they are detected. This makes detailed diagnostics messages, and hence debugging, difficult.

??? example

    ```cpp
    --8<-- "examples/diagnostics_standard.cpp"
    ```
    
    Output:

    ```
    --8<-- "examples/diagnostics_standard.output"
    ```

    This exception can be hard to debug if storing the value `#!c "12"` and accessing it is further apart.

To create better diagnostics messages, each JSON value needs a pointer to its parent value such that a global context (i.e., a path from the root value to the value that led to the exception) can be created. That global context is provided as [JSON Pointer](../features/json_pointer.md).

As this global context comes at the price of storing one additional pointer per JSON value and runtime overhead to maintain the parent relation, extended diagnostics are disabled by default. They can, however, be enabled by defining the preprocessor symbol [`JSON_DIAGNOSTICS`](../api/macros/json_diagnostics.md) to `1` before including `json.hpp`.

??? example

    ```cpp
    --8<-- "examples/diagnostics_extended.cpp"
    ```
    
    Output:

    ```
    --8<-- "examples/diagnostics_extended.output"
    ```

    Now the exception message contains a JSON Pointer `/address/housenumber` that indicates which value has the wrong type.

See [documentation of `JSON_DIAGNOSTICS`](../api/macros/json_diagnostics.md) for more information.

## Parse errors

The library throws this exception when a parse error occurs. Parse errors
can occur during the deserialization of JSON text, CBOR, MessagePack, as well
as when using JSON Patch.

Exceptions have ids 1xx.

!!! info "Byte index"

    Member `byte` holds the byte index of the last read character in the input
    file.

    For an input with n bytes, 1 is the index of the first character and n+1
    is the index of the terminating null byte or the end of file. This also
    holds true when reading a byte vector (CBOR or MessagePack).

??? example

    The following code shows how a `parse_error` exception can be caught.

    ```cpp
    --8<-- "examples/parse_error.cpp"
    ```
    
    Output:

    ```
    --8<-- "examples/parse_error.output"
    ```


### json.exception.parse_error.101

This error indicates a syntax error while deserializing a JSON text. The error message describes that an unexpected token (character) was encountered, and the member `byte` indicates the error position.

!!! failure "Example message"

    Input ended prematurely:

    ```
    [json.exception.parse_error.101] parse error at 2: unexpected end of input; expected string literal
    ```

    No input:

    ```
    [json.exception.parse_error.101] parse error at line 1, column 1: attempting to parse an empty input; check that your input string or stream contains the expected JSON
    ```

    Control character was not escaped:

    ```
    [json.exception.parse_error.101] parse error at line 1, column 2: syntax error while parsing value - invalid string: control character U+0009 (HT) must be escaped to \u0009 or \\; last read: '"'"
    ```

    String was not closed:

    ```
    [json.exception.parse_error.101] parse error at line 1, column 2: syntax error while parsing value - invalid string: missing closing quote; last read: '"'
    ```

    Invalid number format:

    ```
    [json.exception.parse_error.101] parse error at line 1, column 3: syntax error while parsing value - invalid number; expected '+', '-', or digit after exponent; last read: '1E'
    ```

    `\u` was not be followed by four hex digits:

    ```
    [json.exception.parse_error.101] parse error at line 1, column 6: syntax error while parsing value - invalid string: '\u' must be followed by 4 hex digits; last read: '"\u01"'
    ```

    Invalid UTF-8 surrogate pair:

    ```
    [json.exception.parse_error.101] parse error at line 1, column 13: syntax error while parsing value - invalid string: surrogate U+DC00..U+DFFF must follow U+D800..U+DBFF; last read: '"\uD7FF\uDC00'"
    ```

    Invalid UTF-8 byte:

    ```
    [json.exception.parse_error.101] parse error at line 3, column 24: syntax error while parsing value - invalid string: ill-formed UTF-8 byte; last read: '"vous \352t'
    ```

!!! tip

    - Make sure the input is correctly read. Try to write the input to standard output to check if, for instance, the input file was successfully opened.
    - Paste the input to a JSON validator like <http://jsonlint.com> or a tool like [jq](https://stedolan.github.io/jq/).

### json.exception.parse_error.102

JSON uses the `\uxxxx` format to describe Unicode characters. Code points above 0xFFFF are split into two `\uxxxx` entries ("surrogate pairs"). This error indicates that the surrogate pair is incomplete or contains an invalid code point.

!!! failure "Example message"

    ```
    parse error at 14: missing or wrong low surrogate
    ```

!!! note

    This exception is not used any more. Instead [json.exception.parse_error.101](#jsonexceptionparse_error101) with a more detailed description is used.

### json.exception.parse_error.103

Unicode supports code points up to 0x10FFFF. Code points above 0x10FFFF are invalid.

!!! failure "Example message"

    ```
    parse error: code points above 0x10FFFF are invalid
    ```

!!! note

    This exception is not used any more. Instead [json.exception.parse_error.101](#jsonexceptionparse_error101) with a more detailed description is used.

### json.exception.parse_error.104

[RFC 6902](https://tools.ietf.org/html/rfc6902) requires a JSON Patch document to be a JSON document that represents an array of objects.

!!! failure "Example message"

    ```
    [json.exception.parse_error.104] parse error: JSON patch must be an array of objects
    ```

### json.exception.parse_error.105

An operation of a JSON Patch document must contain exactly one "op" member, whose value indicates the operation to perform. Its value must be one of "add", "remove", "replace", "move", "copy", or "test"; other values are errors.

!!! failure "Example message"

    ```
    [json.exception.parse_error.105] parse error: operation 'add' must have member 'value'
    ```
    ```
    [json.exception.parse_error.105] parse error: operation 'copy' must have string member 'from'
    ```
    ```
    [json.exception.parse_error.105] parse error: operation value 'foo' is invalid
    ```

### json.exception.parse_error.106

An array index in a JSON Pointer ([RFC 6901](https://tools.ietf.org/html/rfc6901)) may be `0` or any number without a leading `0`.

!!! failure "Example message"

    ```
    [json.exception.parse_error.106] parse error: array index '01' must not begin with '0'
    ```

### json.exception.parse_error.107

A JSON Pointer must be a Unicode string containing a sequence of zero or more reference tokens, each prefixed by a `/` character.

!!! failure "Example message"

    ```
    [json.exception.parse_error.107] parse error at byte 1: JSON pointer must be empty or begin with '/' - was: 'foo'
    ```

### json.exception.parse_error.108

In a JSON Pointer, only `~0` and `~1` are valid escape sequences.

!!! failure "Example message"

    ```
    [json.exception.parse_error.108] parse error: escape character '~' must be followed with '0' or '1'
    ```

### json.exception.parse_error.109

A JSON Pointer array index must be a number.

!!! failure "Example messages"

    ```
    [json.exception.parse_error.109] parse error: array index 'one' is not a number
    ```
    ```
    [json.exception.parse_error.109] parse error: array index '+1' is not a number
    ```

### json.exception.parse_error.110

When parsing a [binary format](../features/binary_formats/index.md), the byte vector ends before the complete value has
been read.

!!! failure "Example messages"

    ```
    [json.exception.parse_error.110] parse error at byte 5: syntax error while parsing CBOR string: unexpected end of input
    ```
    ```
    [json.exception.parse_error.110] parse error at byte 2: syntax error while parsing UBJSON value: expected end of input; last byte: 0x5A
    ```
    ```
    [json.exception.parse_error.110] parse error at byte 8: syntax error while parsing BSON number: unexpected end of input
    ```

### json.exception.parse_error.112

An unexpected byte was read in a [binary format](../features/binary_formats/index.md) or length information is invalid ([BSON](../features/binary_formats/bson.md)).

!!! failure "Example messages"

    ```
    [json.exception.parse_error.112] parse error at byte 1: syntax error while parsing CBOR value: invalid byte: 0x1C
    ```
    ```
    [json.exception.parse_error.112] parse error at byte 1: syntax error while parsing MessagePack value: invalid byte: 0xC1
    ```
    ```
    [json.exception.parse_error.112] parse error at byte 4: syntax error while parsing BJData size: expected '#' after type information; last byte: 0x02
    ```
    ```
    [json.exception.parse_error.112] parse error at byte 4: syntax error while parsing UBJSON size: expected '#' after type information; last byte: 0x02
    ```
    ```
    [json.exception.parse_error.112] parse error at byte 10: syntax error while parsing BSON string: string length must be at least 1, is -2147483648
    ```
    ```
    [json.exception.parse_error.112] parse error at byte 15: syntax error while parsing BSON binary: byte array length cannot be negative, is -1
    ```
    ```
    [json.exception.parse_error.112] parse error at byte 9: syntax error while parsing CBOR value: negative integer overflow
    ```
    ```
    [json.exception.parse_error.112] parse error at byte 5: syntax error while parsing BSON document: document size 6 does not match the number of bytes read (5)
    ```

### json.exception.parse_error.113

A string could not be read from a [binary format](../features/binary_formats/index.md): either a value that is not a
string was read where one was required (for instance as a map key), or the string's length specification is invalid.

!!! failure "Example messages"

    ```
    [json.exception.parse_error.113] parse error at byte 2: syntax error while parsing CBOR string: expected length specification (0x60-0x7B) or indefinite string type (0x7F); last byte: 0xFF
    ```
    ```
    [json.exception.parse_error.113] parse error at byte 2: syntax error while parsing MessagePack string: expected length specification (0xA0-0xBF, 0xD9-0xDB); last byte: 0xFF
    ```
    ```
    [json.exception.parse_error.113] parse error at byte 2: syntax error while parsing UBJSON char: byte after 'C' must be in range 0x00..0x7F; last byte: 0x82
    ```
    ```
    [json.exception.parse_error.113] parse error at byte 3: syntax error while parsing BJData string: string length must not be negative
    ```

### json.exception.parse_error.114

The parsing of the corresponding BSON record type is not implemented (yet).

!!! failure "Example message"

    ```
    [json.exception.parse_error.114] parse error at byte 5: Unsupported BSON record type 0xFF
    ```

### json.exception.parse_error.115

A UBJSON high-precision number could not be parsed.

!!! failure "Example message"

    ```
    [json.exception.parse_error.115] parse error at byte 5: syntax error while parsing UBJSON high-precision number: invalid number text: 1A
    ```

## Iterator errors

This exception is thrown if iterators passed to a library function do not match
the expected semantics.

Exceptions have ids 2xx.

??? example

    The following code shows how an `invalid_iterator` exception can be caught.

    ```cpp
    --8<-- "examples/invalid_iterator.cpp"
    ```
    
    Output:

    ```
    --8<-- "examples/invalid_iterator.output"
    ```

### json.exception.invalid_iterator.201

The iterators passed to constructor `basic_json(InputIT first, InputIT last)` are not compatible, meaning they do not belong to the same container. Therefore, the range (`first`, `last`) is invalid.

!!! failure "Example message"

    ```
    [json.exception.invalid_iterator.201] iterators are not compatible
    ```

### json.exception.invalid_iterator.202

In the [erase](../api/basic_json/erase.md) or insert function, the passed iterator `pos` does not belong to the JSON value for which the function was called. It hence does not define a valid position for the deletion/insertion.

!!! failure "Example messages"

    ```
    [json.exception.invalid_iterator.202] iterator does not fit current value
    ```
    ```
    [json.exception.invalid_iterator.202] iterators first and last must point to objects
    ```

### json.exception.invalid_iterator.203

Either iterator passed to function [`erase(IteratorType first, IteratorType last`)](../api/basic_json/erase.md) does not belong to the JSON value from which values shall be erased. It hence does not define a valid range to delete values from.

!!! failure "Example message"

    ```
    [json.exception.invalid_iterator.203] iterators do not fit current value
    ```

### json.exception.invalid_iterator.204

When an iterator range for a primitive type (number, boolean, or string) is passed to a constructor or an [erase](../api/basic_json/erase.md) function, this range has to be exactly (`begin(),` `end()),` because this is the only way the single stored value is expressed. All other ranges are invalid.

!!! failure "Example message"

    ```
    [json.exception.invalid_iterator.204] iterators out of range
    ```

### json.exception.invalid_iterator.205

When an iterator for a primitive type (number, boolean, or string) is passed to an [erase](../api/basic_json/erase.md) function, the iterator has to be the `begin()` iterator, because it is the only way to address the stored value. All other iterators are invalid.

!!! failure "Example message"

    ```
    [json.exception.invalid_iterator.205] iterator out of range
    ```

### json.exception.invalid_iterator.206

The iterators passed to constructor `basic_json(InputIT first, InputIT last)` belong to a JSON null value and hence to not define a valid range.

!!! failure "Example message"

    ```
    [json.exception.invalid_iterator.206] cannot construct with iterators from null
    ```

### json.exception.invalid_iterator.207

The `key()` member function can only be used on iterators belonging to a JSON object, because other types do not have a concept of a key.

!!! failure "Example message"

    ```
    [json.exception.invalid_iterator.207] cannot use key() for non-object iterators
    ```


### json.exception.invalid_iterator.208

The `operator[]` to specify a concrete offset cannot be used on iterators belonging to a JSON object, because JSON objects are unordered.

!!! failure "Example message"

    ```
    [json.exception.invalid_iterator.208] cannot use operator[] for object iterators
    ```

### json.exception.invalid_iterator.209

The offset operators (`+`, `-`, `+=`, `-=`) cannot be used on iterators belonging to a JSON object, because JSON objects are unordered.

!!! failure "Example message"

    ```
    [json.exception.invalid_iterator.209] cannot use offsets with object iterators
    ```

### json.exception.invalid_iterator.210

The iterator range passed to the insert function is not compatible, meaning they do not belong to the same container. Therefore, the range (`first`, `last`) is invalid.

!!! failure "Example message"

    ```
    [json.exception.invalid_iterator.210] iterators do not fit
    ```

### json.exception.invalid_iterator.211

The iterator range passed to the insert function must not be a subrange of the container to insert to.

!!! failure "Example message"

    ```
    [json.exception.invalid_iterator.211] passed iterators may not belong to container
    ```

### json.exception.invalid_iterator.212

When two iterators are compared, they must belong to the same container.

!!! failure "Example message"

    ```
    [json.exception.invalid_iterator.212] cannot compare iterators of different containers
    ```

### json.exception.invalid_iterator.213

The order of object iterators cannot be compared, because JSON objects are unordered.

!!! failure "Example message"

    ```
    [json.exception.invalid_iterator.213] cannot compare order of object iterators
    ```

### json.exception.invalid_iterator.214

Cannot retrieve value from iterator: The iterator either refers to a null value, or it refers to a primitive type (number, boolean, or string), but does not match the iterator returned by `begin()`.

!!! failure "Example message"

    ```
    [json.exception.invalid_iterator.214] cannot get value
    ```

## Type errors

This exception is thrown in case of a type error; that is, a library function is executed on a JSON value whose type does not match the expected semantics.

Exceptions have ids 3xx.

??? example

    The following code shows how a `type_error` exception can be caught.

    ```cpp
    --8<-- "examples/type_error.cpp"
    ```
    
    Output:

    ```
    --8<-- "examples/type_error.output"
    ```

### json.exception.type_error.301

To create an object from an initializer list, the initializer list must consist only of a list of pairs whose first element is a string. When this constraint is violated, an array is created instead.

!!! failure "Example message"

    ```
    [json.exception.type_error.301] cannot create object from initializer list
    ```

### json.exception.type_error.302

During implicit or explicit value conversion, the JSON type must be compatible with the target type. For instance, a JSON string can only be converted into string types, but not into numbers or boolean types.

!!! failure "Example messages"

    ```
    [json.exception.type_error.302] type must be object, but is null
    ```
    ```
    [json.exception.type_error.302] type must be string, but is object
    ```

### json.exception.type_error.303

To retrieve a reference to a value stored in a `basic_json` object with `get_ref`, the type of the reference must match the value type. For instance, for a JSON array, the `ReferenceType` must be `array_t &`.

!!! failure "Example messages"

    ```
    [json.exception.type_error.303] incompatible ReferenceType for get_ref, actual type is object
    ```
    ```
    [json.exception.type_error.303] incompatible ReferenceType for get_ref, actual type is number"
    ```

### json.exception.type_error.304

The `at()` member functions can only be executed for certain JSON types.

!!! failure "Example messages"

    ```
    [json.exception.type_error.304] cannot use at() with string
    ```
    ```
    [json.exception.type_error.304] cannot use at() with number
    ```

### json.exception.type_error.305

The `operator[]` member functions can only be executed for certain JSON types.

!!! failure "Example messages"

    ```
    [json.exception.type_error.305] cannot use operator[] with a string argument with array
    ```
    ```
    [json.exception.type_error.305] cannot use operator[] with a numeric argument with object
    ```

### json.exception.type_error.306

The `value()` member functions can only be executed for certain JSON types.

!!! failure "Example message"

    ```
    [json.exception.type_error.306] cannot use value() with number
    ```

### json.exception.type_error.307

The [`erase()`](../api/basic_json/erase.md) member functions can only be executed for certain JSON types.

!!! failure "Example message"

    ```
    [json.exception.type_error.307] cannot use erase() with string
    ```

### json.exception.type_error.308

The `push_back()` and `operator+=` member functions can only be executed for certain JSON types.

!!! failure "Example message"

    ```
    [json.exception.type_error.308] cannot use push_back() with string
    ```

### json.exception.type_error.309

The `insert()` member functions can only be executed for certain JSON types.

!!! failure "Example messages"

    ```
    [json.exception.type_error.309] cannot use insert() with array
    ```
    ```
    [json.exception.type_error.309] cannot use insert() with number
    ```

### json.exception.type_error.310

The `swap()` member functions can only be executed for certain JSON types.

!!! failure "Example message"

    ```
    [json.exception.type_error.310] cannot use swap() with number
    ```

### json.exception.type_error.311

The `emplace()` and `emplace_back()` member functions can only be executed for certain JSON types.

!!! failure "Example messages"

    ```
    [json.exception.type_error.311] cannot use emplace() with number
    ```
    ```
    [json.exception.type_error.311] cannot use emplace_back() with number
    ```

### json.exception.type_error.312

The `update()` member functions can only be executed for certain JSON types.

!!! failure "Example message"

    ```
    [json.exception.type_error.312] cannot use update() with array
    ```

### json.exception.type_error.313

The `unflatten` function converts an object whose keys are JSON Pointers back into an arbitrary nested JSON value. The JSON Pointers must not overlap, because then the resulting value would not be well-defined.

!!! failure "Example message"

    ```
    [json.exception.type_error.313] invalid value to unflatten
    ```

### json.exception.type_error.314

The `unflatten` function only works for an object whose keys are JSON Pointers.

!!! failure "Example message"

    Calling `unflatten()` on an array `#!json [1,2,3]`:

    ```
    [json.exception.type_error.314] only objects can be unflattened
    ```

### json.exception.type_error.315

The `unflatten()` function only works for an object whose keys are JSON Pointers and whose values are primitive.

!!! failure "Example message"

    Calling `unflatten()` on an object `#!json {"/1", [1,2,3]}`:

    ```
    [json.exception.type_error.315] values in object must be primitive
    ```

### json.exception.type_error.316

The `dump()` function only works with UTF-8 encoded strings; that is, if you assign a `std::string` to a JSON value, make sure it is UTF-8 encoded.

!!! failure "Example message"

    Calling `dump()` on a JSON value containing an ISO 8859-1 encoded string:
    ```
    [json.exception.type_error.316] invalid UTF-8 byte at index 15: 0x6F
    ```

!!! tip

    - Store the source file with UTF-8 encoding.
    - Pass an error handler as last parameter to the `dump()` function to avoid this exception:
        - `json::error_handler_t::replace` will replace invalid bytes sequences with `U+FFFD` 
        - `json::error_handler_t::ignore` will silently ignore invalid byte sequences

### json.exception.type_error.317

The dynamic type of the object cannot be represented in the requested serialization format (e.g., a raw `true` or `null` JSON object cannot be serialized to BSON)

!!! failure "Example messages"

    Serializing `#!json null` to BSON:
    ```
    [json.exception.type_error.317] to serialize to BSON, top-level type must be object, but is null
    ```
    Serializing `#!json [1,2,3]` to BSON:
    ```
    [json.exception.type_error.317] to serialize to BSON, top-level type must be object, but is array
    ```

!!! tip

    Encapsulate the JSON value in an object. That is, instead of serializing `#!json true`, serialize `#!json {"value": true}`

## Out of range

This exception is thrown in case a library function is called on an input parameter that exceeds the expected range, for instance, in the case of array indices or nonexisting object keys.

Exceptions have ids 4xx.

??? example

    The following code shows how an `out_of_range` exception can be caught.

    ```cpp
    --8<-- "examples/out_of_range.cpp"
    ```
    
    Output:

    ```
    --8<-- "examples/out_of_range.output"
    ```

### json.exception.out_of_range.401

The provided array index `i` is larger than `size-1`.

!!! failure "Example message"

    ```
    array index 3 is out of range
    ```

### json.exception.out_of_range.402

The special array index `-` in a JSON Pointer never describes a valid element of the array, but the index past the end. That is, it can only be used to add elements at this position, but not to read it.

!!! failure "Example message"

    ```
    array index '-' (3) is out of range
    ```

### json.exception.out_of_range.403

The provided key was not found in the JSON object.

!!! failure "Example message"

    ```
    key 'foo' not found
    ```

### json.exception.out_of_range.404

A reference token in a JSON Pointer could not be resolved.

!!! failure "Example message"

    ```
    unresolved reference token 'foo'
    ```

### json.exception.out_of_range.405

The JSON Patch operations 'remove' and 'add' cannot be applied to the root element of the JSON value.

!!! failure "Example message"

    ```
    JSON pointer has no parent
    ```

### json.exception.out_of_range.406

A parsed number could not be stored as without changing it to NaN or INF.

!!! failure "Example message"

    ```
    number overflow parsing '10E1000'
    ```

### json.exception.out_of_range.407

This exception previously indicated that the UBJSON and BSON binary formats did not support integer numbers greater than
9223372036854775807 due to limitations in the implemented mapping. However, these limitations have since been resolved,
and this exception no longer occurs.

!!! success "Exception cannot occur any more"

    - Since version 3.9.0, integer numbers beyond int64 are serialized as high-precision UBJSON numbers.
    - Since version 3.12.0, integer numbers beyond int64 are serialized as uint64 BSON numbers.

### json.exception.out_of_range.408

The size of an array or object in a [binary format](../features/binary_formats/index.md) exceeds the maximal capacity:
the size following `#` for [UBJSON](../features/binary_formats/ubjson.md)/[BJData](../features/binary_formats/bjdata.md),
or the encoded length for [CBOR](../features/binary_formats/cbor.md).

!!! failure "Example messages"

    ```
    excessive array size: 8658170730974374167
    ```
    ```
    [json.exception.out_of_range.408] syntax error while parsing CBOR size: excessive array size
    ```
    ```
    [json.exception.out_of_range.408] syntax error while parsing CBOR size: excessive map size
    ```

### json.exception.out_of_range.409

Key identifiers to be serialized to BSON cannot contain code point U+0000, since the key is stored as zero-terminated c-string.

!!! failure "Example message"

    ```
    BSON key cannot contain code point U+0000 (at byte 2)
    ```

### json.exception.out_of_range.410

This exception is thrown when an undefined value is used with
[`NLOHMANN_JSON_SERIALIZE_ENUM_STRICT`](../api/macros/nlohmann_json_serialize_enum_strict.md), or when an array index in
a JSON pointer exceeds the range of `size_type` (e.g., on 32-bit platforms).

!!! failure "Example message"

    ```
    enum value out of range
    array index 18446744073709551616 exceeds size_type
    ```

### json.exception.out_of_range.411

A JSON Patch `add` operation cannot be applied because the target location's parent is neither an object nor an array. Per [RFC 6902](https://datatracker.ietf.org/doc/html/rfc6902), an `add` target must reference a member of an existing object or an element of an existing array; a primitive value (string, number, boolean, etc.) cannot receive a new member or element.

!!! failure "Example message"

    ```
    cannot add value: the JSON Patch 'add' target's parent is of type string, but must be an object or array
    ```

!!! note

    This exception was added in version 3.13.0. Before that, this situation hit an internal assertion (aborting the program in debug builds) or was silently ignored when assertions were disabled.

### json.exception.out_of_range.412

BSON stores the length of documents, arrays, strings, and binary values in a signed 32-bit integer. This exception is thrown when a value is too large to be described by such a length field.

!!! failure "Example message"

    ```
    BSON length 2147483661 exceeds maximum of 2147483647
    ```

!!! note

    This exception was added in version 3.13.0. Before that, the length was silently truncated, and
    [`to_bson`](../api/basic_json/to_bson.md) produced documents with negative length prefixes that
    [`from_bson`](../api/basic_json/from_bson.md) rejected.

## Further exceptions

This exception is thrown in case of errors that cannot be classified with the
other exception types.

Exceptions have ids 5xx.

??? example

    The following code shows how an `other_error` exception can be caught.

    ```cpp
    --8<-- "examples/other_error.cpp"
    ```
    
    Output:

    ```
    --8<-- "examples/other_error.output"
    ```

### json.exception.other_error.501

A JSON Patch operation 'test' failed. The unsuccessful operation is also printed.

!!! failure "Example message"

    Executing `#!json {"op":"test", "path":"/baz", "value":"bar"}` on `#!json {"baz": "qux"}`:

    ```
    [json.exception.other_error.501] unsuccessful: {"op":"test","path":"/baz","value":"bar"}
    ```

---

## File: docs/mkdocs/docs/home/faq.md

# Frequently Asked Questions (FAQ)

## Known bugs

### Brace initialization yields arrays

!!! question

    Why does

    ```cpp
    json j{true};
    ```

    and

    ```cpp
    json j(true);
    ```

    yield different results (`#!json [true]` vs. `#!json true`)?

This is a known issue, and -- even worse -- the behavior differs between GCC and Clang. The "culprit" for this is the library's constructor overloads for initializer lists to allow syntax like

```cpp
json array = {1, 2, 3, 4};
```

for arrays and

```cpp
json object = {{"one", 1}, {"two", 2}}; 
```

for objects.

!!! tip

    To avoid any confusion and ensure portable code, **do not** use brace initialization with the types `basic_json`, `json`, or `ordered_json` unless you want to create an object or array as shown in the examples above.

    To explicitly create a single-element array, use `json::array({value})`:

    ```cpp
    json j = json::array({true});  // [true]
    ```

**Opt-in copy semantics (since version 3.12.0)**

If you define `JSON_BRACE_INIT_COPY_SEMANTICS` to `1` before including the library, single-element brace initialization is treated as copy/move instead of creating a single-element array:

```cpp
#define JSON_BRACE_INIT_COPY_SEMANTICS 1
#include <nlohmann/json.hpp>

json obj = {{"key", "value"}};
json j{obj};   // -> {"key":"value"}  (copy, not array)
```

Without the macro (default behavior), `json j{obj}` creates `[{"key":"value"}]`. This opt-in macro fixes issue #5074 while preserving backwards compatibility for existing code.

## Limitations

### Relaxed parsing

!!! question

    Can you add an option to ignore trailing commas?

This library does not support any feature that would jeopardize interoperability.


### Parse errors reading non-ASCII characters

!!! question "Questions"

    - Why is the parser complaining about a Chinese character?
    - Does the library support Unicode?
    - I get an exception `[json.exception.parse_error.101] parse error at line 1, column 53: syntax error while parsing value - invalid string: ill-formed UTF-8 byte; last read: '"Testé$')"`

The library supports **Unicode input** as follows:

- Only **UTF-8** encoded input is supported, which is the default encoding for JSON, according to [RFC 8259](https://tools.ietf.org/html/rfc8259.html#section-8.1).
- `std::u16string` and `std::u32string` can be parsed, assuming UTF-16 and UTF-32 encoding, respectively. These encodings are not supported when reading from files or other input containers.
- Other encodings such as Latin-1 or ISO 8859-1 are **not** supported and will yield parse or serialization errors.
- The library will not replace [Unicode noncharacters](http://www.unicode.org/faq/private_use.html#nonchar1).
- Invalid surrogates (e.g., incomplete pairs such as `\uDEAD`) will yield parse errors.
- The strings stored in the library are UTF-8 encoded. When using the default string type (`std::string`), note that its length/size functions return the number of stored bytes rather than the number of characters or glyphs.
- When you store strings with different encodings in the library, calling [`dump()`](https://nlohmann.github.io/json/classnlohmann_1_1basic__json_a50ec80b02d0f3f51130d4abb5d1cfdc5.html#a50ec80b02d0f3f51130d4abb5d1cfdc5) may throw an exception unless `json::error_handler_t::replace` or `json::error_handler_t::ignore` are used as error handlers.

In most cases, the parser is right to complain, because the input is not UTF-8 encoded. This is especially true for Microsoft Windows, where Latin-1 or ISO 8859-1 is often the standard encoding.


### Wide string handling

!!! question

    Why are wide strings (e.g., `std::wstring`) dumped as arrays of numbers?

As described [above](#parse-errors-reading-non-ascii-characters), the library assumes UTF-8 as encoding.  To store a wide string, you need to change the encoding.

!!! example

    ```cpp
    #include <codecvt> // codecvt_utf8
    #include <locale>  // wstring_convert
    
    // encoding function
    std::string to_utf8(std::wstring& wide_string)
    {
        static std::wstring_convert<std::codecvt_utf8<wchar_t>> utf8_conv;
        return utf8_conv.to_bytes(wide_string);
    }
    
    json j;
    std::wstring ws = L"車B1234 こんにちは";
    
    j["original"] = ws;
    j["encoded"] = to_utf8(ws);
    
    std::cout << j << std::endl;
    ```
    
    The result is:
    
    ```json
    {
      "encoded": "車B1234 こんにちは",
      "original": [36554, 66, 49, 50, 51, 52, 32, 12371, 12435, 12395, 12385, 12399]
    }
    ```

## Usage

### Thread safety

!!! question

    Is `basic_json` thread-safe?

No. `basic_json` provides no built-in synchronization, the same as `std::map` or `std::vector`. Concurrent reads of
the same value from multiple threads are safe, as are concurrent (non-overlapping) accesses to independent `json`
objects. However, any concurrent write to a `json` object -- or a concurrent read while another thread writes to the
same object -- is a data race and requires external synchronization (e.g., a `std::mutex`) by the caller.

### Schema validation

!!! question

    Does this library support JSON Schema validation?

Not directly, but the companion project [json-schema-validator](https://github.com/pboettch/json-schema-validator)
builds JSON Schema (draft 4, 6, 7, and 2019-09) validation on top of this library and is a common recommendation
for this use case.

## Exceptions

### Parsing without exceptions

!!! question

    Is it possible to indicate a parse error without throwing an exception?

Yes, see [Parsing and exceptions](../features/parsing/parse_exceptions.md).


### Key name in exceptions

!!! question

    Can I get the key of the object item that caused an exception?

Yes, you can. Please define the symbol [`JSON_DIAGNOSTICS`](../api/macros/json_diagnostics.md) to get [extended diagnostics messages](exceptions.md#extended-diagnostic-messages).


## Serialization issues


### Number precision

!!! question

    - It seems that precision is lost when serializing a double.
    - Can I change the precision for floating-point serialization?

The library uses `std::numeric_limits<number_float_t>::digits10` (15 for IEEE `double`s) digits for serialization. This value is sufficient to guarantee roundtripping. If one uses more than this number of digits of precision, then string -> value -> string is not guaranteed to round-trip.

!!! quote "[cppreference.com](https://en.cppreference.com/w/cpp/types/numeric_limits/digits10)"

    The value of `std::numeric_limits<T>::digits10` is the number of base-10 digits that can be represented by the type T without change, that is, any number with this many significant decimal digits can be converted to a value of type T and back to decimal form, without change due to rounding or overflow. 

!!! tip

    The website https://float.exposed gives a good insight into the internal storage of floating-point numbers.

See [this section](../features/types/number_handling.md#number-serialization) on the library's number handling for more information.

### Serializing untrusted or invalid UTF-8

!!! question "Questions"

    - Why does `dump()` throw when I serialize data that came from the network?
    - Is CVE-2024-34363 a vulnerability in this library?

Crashes reported against this library that stem from an uncaught
[`type_error.316`](exceptions.md#jsonexceptiontype_error316) while serializing unvalidated input (e.g.,
CVE-2024-34363) are a usage issue, not a library vulnerability:
[`dump()`](../api/basic_json/dump.md) throws in its default `strict` mode because
[RFC 8259](https://datatracker.ietf.org/doc/html/rfc8259#section-8.1) requires JSON text to be valid UTF-8.

The recommended pattern is to pass a non-strict [`error_handler`](../api/basic_json/error_handler_t.md) or to handle the
exception:

```cpp
// replace invalid sequences with U+FFFD instead of throwing
const auto s = j.dump(-1, ' ', false, json::error_handler_t::replace);
```

### Using JSON values with `std::format` or `fmt`

!!! question

    - Can I use `std::format("{}", j)` on a JSON value?
    - Can I use `fmt::format("{}", j)` or `fmt::print("{}", j)` (the [{fmt}](https://github.com/fmtlib/fmt) library) on a JSON value?

`std::format` works out of the box since version 3.13.0, as long as the standard library provides
`<format>` (see [`JSON_HAS_STD_FORMAT`](../api/macros/json_has_std_format.md)); see
[`std::formatter`](../api/basic_json/std_formatter.md) for details, including the `#!cpp "{:#}"`
pretty-print spec, indent widths (`#!cpp "{:2}"`), and custom indent characters (`#!cpp "{:.>#}"`).

For `fmt`, the library ships [`format_as`](../api/basic_json/format_as.md), a small customization point
`fmt` looks for via argument-dependent lookup. It only has an effect on fmt 10.0.0 through 11.0.2 — from
fmt 11.1.0 onwards, `fmt` no longer picks up a `format_as` overload that returns a `std::string`. On such
versions (or any version, if you also want the same `#!cpp "{:#}"`/width/fill-and-align spec support that
`std::formatter` has), define your own `fmt::formatter` specialization; see
[`format_as`](../api/basic_json/format_as.md) for a recipe that mirrors it.

If you get ambiguous-overload errors when passing a JSON value to `fmt::format`/`fmt::print` without any
`fmt::formatter<json>` specialization in scope, that's `fmt` picking up `basic_json`'s implicit
`operator ValueType()` conversion operator (see [#964](https://github.com/nlohmann/json/issues/964) and
[#958](https://github.com/nlohmann/json/issues/958)); disabling it via
[`JSON_USE_IMPLICIT_CONVERSIONS 0`](../api/macros/json_use_implicit_conversions.md) avoids the ambiguity.

## Compilation issues

### Android SDK

!!! question

    Why does the code not compile with Android SDK?

Android defaults to using very old compilers and C++ libraries. To fix this, add the following to your `Application.mk`. This will switch to the LLVM C++ library, the Clang compiler, and enable C++11 and other features disabled by default.

```ini
APP_STL := c++_shared
NDK_TOOLCHAIN_VERSION := clang3.6
APP_CPPFLAGS += -frtti -fexceptions
```

The code compiles successfully with [Android NDK](https://developer.android.com/ndk/index.html?hl=ml), Revision 9 - 11 (and possibly later) and [CrystaX's Android NDK](https://www.crystax.net/en/android/ndk) version 10.


### Missing STL function

!!! question "Questions"

    - Why do I get a compilation error `'to_string' is not a member of 'std'` (or similarly, for `strtod` or `strtof`)?
    - Why does the code not compile with MinGW or Android SDK?

This is not an issue with the code, but rather with the compiler itself. On Android, see above to build with a newer environment.  For MinGW, please refer to [this site](http://tehsausage.com/mingw-to-string) and [this discussion](https://github.com/nlohmann/json/issues/136) for information on how to fix this bug. For Android NDK using `APP_STL := gnustl_static`, please refer to [this discussion](https://github.com/nlohmann/json/issues/219).

---

## File: docs/mkdocs/docs/home/releases.md

# Releases

This page summarizes the notable changes of every release and links to the relevant documentation.
The **complete release notes** — including all changes, the download files, and their checksums — are
published on the [GitHub releases page](https://github.com/nlohmann/json/releases).

## v3.12.0 (2025-04-11)

Fixes bugs found in 3.11.3 and adds several features. All changes are backward-compatible.

- Adds diagnostic byte positions via [`JSON_DIAGNOSTIC_POSITIONS`](../api/macros/json_diagnostic_positions.md),
  exposed through the new [`start_pos`](../api/basic_json/start_pos.md) and
  [`end_pos`](../api/basic_json/end_pos.md) member functions.
- Makes the [conversion macros](../features/arbitrary_types.md#simplify-your-life-with-macros)
  templated (so they also work with [`ordered_json`](../api/ordered_json.md)) and adds
  [`NLOHMANN_DEFINE_DERIVED_TYPE`](../api/macros/nlohmann_define_derived_type.md) for derived classes.
- Adds `std::optional` support (C++17) and lets [`patch`](../api/basic_json/patch.md),
  [`diff`](../api/basic_json/diff.md), and [`flatten`](../api/basic_json/flatten.md) work with
  arbitrary string types.
- Extends the [binary formats](../features/binary_formats/index.md):
  [BJData](../features/binary_formats/bjdata.md) draft 3 and unsigned 64-bit integers for
  [BSON](../features/binary_formats/bson.md).
- Adds multidimensional C-array conversion and UTF-8 encoded `std::filesystem::path` conversions, and
  lowers the minimum [CMake](../integration/cmake.md) version to allow CMake 4.0.

[Full release notes](https://github.com/nlohmann/json/releases/tag/v3.12.0).

## v3.11.3 (2023-11-28)

Adds features and fixes bugs found in 3.11.2. All changes are backward-compatible.

- Adds a [custom base class](../api/basic_json/json_base_class_t.md) as a node customization point.
- Adds serialization-only [conversion macros](../features/macros.md)
  (`NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE` and `NLOHMANN_DEFINE_TYPE_INTRUSIVE_ONLY_SERIALIZE`)
  and a clearer parse error for empty input.
- Adds [Bazel](../integration/package_managers.md#bazel) and
  [Swift Package Manager](../integration/package_managers.md#swift-package-manager) build support.
- Fixes custom allocators, a memory leak in [`adl_serializer`](../api/adl_serializer/to_json.md)'s
  `to_json`, initializer-list construction when `size_type` is not `int`, and many compiler warnings.

[Full release notes](https://github.com/nlohmann/json/releases/tag/v3.11.3).

## v3.11.2 (2022-08-12)

Fixes bugs found in 3.11.1 and restructures the namespace. All changes are backward-compatible.

- Fixes the [`value`](../api/basic_json/value.md) function (broken for strings, size types, and
  `nullptr` in 3.11.0) and makes `json_fwd.hpp` self-contained.
- Restores using [`json_pointer`](../api/json_pointer/index.md) as a key in associative containers and
  comparing it with strings.
- Restructures the inline [namespace](../features/namespace.md) and allows disabling the version
  component, and avoids heap allocations in the [BJData](../features/binary_formats/bjdata.md) parser.

[Full release notes](https://github.com/nlohmann/json/releases/tag/v3.11.2).

## v3.11.1 (2022-08-01)

Fixes a regression from 3.11.0. All changes are backward-compatible.

- Restores the global [user-defined string literals](../api/macros/json_use_global_udls.md)
  [`operator""_json`](../api/operator_literal_json.md) and
  [`operator""_json_pointer`](../api/operator_literal_json_pointer.md), which 3.11.0 had moved into a
  namespace by default.

[Full release notes](https://github.com/nlohmann/json/releases/tag/v3.11.1).

## v3.11.0 (2022-08-01)

One of the largest releases ever. All changes are backward-compatible.

- Allows `std::string_view` as object keys in [`at`](../api/basic_json/at.md),
  [`operator[]`](../api/basic_json/operator%5B%5D.md), [`value`](../api/basic_json/value.md),
  [`erase`](../api/basic_json/erase.md), [`find`](../api/basic_json/find.md),
  [`contains`](../api/basic_json/contains.md), and [`count`](../api/basic_json/count.md).
- Adds the [BJData](../features/binary_formats/bjdata.md) binary format (the fifth supported format).
- Improves C++20 support, including [`operator<=>`](../api/basic_json/operator_spaceship.md) and
  `<ranges>`-compatible iterators.
- Adds a versioned, ABI-tagged inline [namespace](../features/namespace.md)
  ([`NLOHMANN_JSON_NAMESPACE`](../api/macros/nlohmann_json_namespace.md)) and the option to move the
  UDLs out of the global namespace ([`JSON_USE_GLOBAL_UDLS`](../api/macros/json_use_global_udls.md)).
- Adds [`patch_inplace`](../api/basic_json/patch_inplace.md), default values for the
  [conversion macros](../features/arbitrary_types.md#simplify-your-life-with-macros), and an option to
  disable enum serialization ([`JSON_DISABLE_ENUM_SERIALIZATION`](../api/macros/json_disable_enum_serialization.md)).

This release introduced a UDL regression that was fixed in
[3.11.1](https://github.com/nlohmann/json/releases/tag/v3.11.1).
[Full release notes](https://github.com/nlohmann/json/releases/tag/v3.11.0).

## v3.10.5 (2022-01-03)

Bug-fix release. All changes are backward-compatible.

- Guards the `std::filesystem` conversions behind compiler-support checks
  ([`JSON_HAS_FILESYSTEM`](../api/macros/json_has_filesystem.md)), which can be set to `0` to disable
  them altogether.

[Full release notes](https://github.com/nlohmann/json/releases/tag/v3.10.5).

## v3.10.4 (2021-10-16)

Fixes regressions introduced in 3.10.0. All changes are backward-compatible.

- Fixes the `std::filesystem::path` conversion (which could trigger a stack overflow and broke
  compilation on Windows).
- Fixes compilation for types with an explicit defaulted constructor and for code relying on the
  return values of `std::find` and `std::remove`.

[Full release notes](https://github.com/nlohmann/json/releases/tag/v3.10.4).

## v3.10.3 (2021-10-08)

Fixes more regressions from 3.10.0. All changes are backward-compatible.

- Fixes [extended-diagnostics](../api/macros/json_diagnostics.md) assertions triggered by
  [`update`](../api/basic_json/update.md) and by inserting into arrays.
- Supports custom allocators when writing binary formats into a `std::vector`, and allows conversion
  from types that only provide `begin()`/`end()`.

[Full release notes](https://github.com/nlohmann/json/releases/tag/v3.10.3).

## v3.10.2 (2021-08-26)

Re-release of 3.10.1, whose Git tag pointed at the wrong commit due to a bug in the release script.
All changes are backward-compatible.
[Full release notes](https://github.com/nlohmann/json/releases/tag/v3.10.2).

## v3.10.1 (2021-08-24)

Fixes a regression from 3.10.0. All changes are backward-compatible.

- Fixes an [extended-diagnostics](../api/macros/json_diagnostics.md) assertion triggered when used
  with [`ordered_json`](../api/ordered_json.md), and hardens the GDB pretty-printer.

[Full release notes](https://github.com/nlohmann/json/releases/tag/v3.10.1).

## v3.10.0 (2021-08-17)

Feature release. All changes are backward-compatible.

- Adds [extended diagnostic messages](../api/macros/json_diagnostics.md)
  ([`JSON_DIAGNOSTICS`](../api/macros/json_diagnostics.md)) that prepend a JSON pointer to exception
  messages to pinpoint the offending value.
- Adds a GDB pretty-printer and a [`cbor_tag_handler_t`](../api/basic_json/cbor_tag_handler_t.md)
  `store` option to keep CBOR tags as binary subtypes.
- Supports containers with non-default-constructible types and parsing from `std::byte`.
- Adds [`JSON_NO_IO`](../api/macros/json_no_io.md) to exclude the I/O headers and the
  [`JSON_HAS_CPP_*`](../api/macros/json_has_cpp_11.md) macros to override the detected C++ standard.

[Full release notes](https://github.com/nlohmann/json/releases/tag/v3.10.0).

## v3.9.1 (2020-08-06)

Fixes two regressions from 3.9.0. All changes are backward-compatible.

- Accepts consecutive [comments](../features/comments.md) and completes the
  [`ordered_json`](../api/ordered_json.md) interface (e.g. `ordered_json::parse`).

[Full release notes](https://github.com/nlohmann/json/releases/tag/v3.9.1).

## v3.9.0 (2020-07-27)

Feature release adding four long-requested features. All changes are backward-compatible.

- Optional [comment](../features/comments.md) parsing in [`parse`](../api/basic_json/parse.md) via the
  `ignore_comments` parameter.
- [`ordered_json`](../api/ordered_json.md) to preserve the [insertion order](../features/object_order.md)
  of object keys.
- An option to switch off [implicit conversions](../api/macros/json_use_implicit_conversions.md).
- The [`NLOHMANN_DEFINE_TYPE_*`](../features/arbitrary_types.md#simplify-your-life-with-macros)
  convenience macros, plus high-precision-number support for
  [UBJSON](../features/binary_formats/ubjson.md) and CBOR tag handling.

[Full release notes](https://github.com/nlohmann/json/releases/tag/v3.9.0).

## v3.8.0 (2020-06-14)

Feature release. All changes are backward-compatible.

- Introduces a [binary value](../features/binary_values.md) type that is read from and written to
  [CBOR](../features/binary_formats/cbor.md), [BSON](../features/binary_formats/bson.md), and
  [MessagePack](../features/binary_formats/messagepack.md), and can be shared between formats.
- Generalizes the input adapters to read from any `LegacyInputIterator` container (3–10 % faster
  parsing).
- Fixes [`contains`](../api/basic_json/contains.md) for JSON pointers and makes the binary
  [`from_cbor`](../api/basic_json/from_cbor.md)/[`from_msgpack`](../api/basic_json/from_msgpack.md)/etc.
  functions respect `allow_exceptions`.

[Full release notes](https://github.com/nlohmann/json/releases/tag/v3.8.0).

## v3.7.3 (2019-11-17)

Fixes a regression from 3.7.2 that could yield quadratic complexity in destructor calls. All changes
are backward-compatible. [Full release notes](https://github.com/nlohmann/json/releases/tag/v3.7.3).

## v3.7.2 (2019-11-10)

Fixes a stack overflow for deeply nested input by making the destructor iterative; parsing is now
bounded only by available memory. All changes are backward-compatible.
[Full release notes](https://github.com/nlohmann/json/releases/tag/v3.7.2).

## v3.7.1 (2019-11-06)

Bug-fix release. All changes are backward-compatible.

- Fixes a segmentation fault when serializing the `std::int64_t` minimum value and fixes
  [`contains`](../api/basic_json/contains.md) for JSON pointers.
- Allows [`items`](../api/basic_json/items.md) with a custom string type and makes `json_pointer::back`
  `const`.

[Full release notes](https://github.com/nlohmann/json/releases/tag/v3.7.1).

## v3.7.0 (2019-07-28)

Convenience features and house-keeping. All changes are backward-compatible.

- Adds a [`contains`](../api/basic_json/contains.md) overload that checks a JSON pointer without
  throwing, a generic `to_string`, and a return value for
  [`emplace_back`](../api/basic_json/emplace_back.md).

[Full release notes](https://github.com/nlohmann/json/releases/tag/v3.7.0).

## v3.6.1 (2019-03-20)

Fixes a regression (GCC 7/8 compilation) and a `<Windows.h>` build error introduced in 3.6.0. All
changes are backward-compatible. [Full release notes](https://github.com/nlohmann/json/releases/tag/v3.6.1).

## v3.6.0 (2019-03-20)

Feature release. All changes are backward-compatible.

- Reworks the [JSON pointer](../features/json_pointer.md) interface (`operator/`, `push_back`,
  `parent_pointer`, …).
- Adds a [`contains`](../api/basic_json/contains.md) function to test for an object key and greatly
  improves the performance of integer serialization.

[Full release notes](https://github.com/nlohmann/json/releases/tag/v3.6.0).

## v3.5.0 (2018-12-22)

Feature release. All changes are backward-compatible.

- Adds structured-binding support via the [`items`](../api/basic_json/items.md) function and reading
  from `FILE*` in the [`parse`](../api/basic_json/parse.md) function.
- Fixes the `eofbit` handling on input streams and a bug in the BSON SAX parser.

[Full release notes](https://github.com/nlohmann/json/releases/tag/v3.5.0).

## v3.4.0 (2018-10-30)

Feature release. All changes are backward-compatible.

- Adds [BSON](../features/binary_formats/bson.md) read/write support.
- Adds configurable Unicode error handlers to [`dump`](../api/basic_json/dump.md) (throw, replace with
  U+FFFD, or ignore) and the
  [`NLOHMANN_JSON_SERIALIZE_ENUM`](../api/macros/nlohmann_json_serialize_enum.md) macro for
  [enum conversion](../features/enum_conversion.md).
- Improves parse-error messages with line/column positions and context.

[Full release notes](https://github.com/nlohmann/json/releases/tag/v3.4.0).

## v3.3.0 (2018-10-05)

Feature release. All changes are backward-compatible.

- Adds GCC 4.8 support, the [`get_to`](../api/basic_json/get_to.md) function, and an overhauled and
  documented [CMake](../integration/cmake.md) integration.

[Full release notes](https://github.com/nlohmann/json/releases/tag/v3.3.0).

## v3.2.0 (2018-08-20)

Feature release. All changes are backward-compatible.

- Adds a [SAX interface](../features/parsing/sax_interface.md) and a non-recursive parser.
- Adds parsing from wide-string types (`std::wstring`, `std::u16string`, `std::u32string`) and
  `std::string_view` (C++17), and round-tripping of `std::map`/`std::unordered_map` with non-string
  keys.

[Full release notes](https://github.com/nlohmann/json/releases/tag/v3.2.0).

## v3.1.2 (2018-03-14)

Bug-fix release. All changes are backward-compatible.

- Fixes a memory leak in the parser callback and adds user-defined string-type support to the parser
  and serializer.

[Full release notes](https://github.com/nlohmann/json/releases/tag/v3.1.2).

## v3.1.1 (2018-02-13)

Bug-fix release. All changes are backward-compatible.

- Fixes parsing of indefinite-length CBOR strings, a user-defined conversion to vector types, and
  overflow detection for UBJSON containers.

[Full release notes](https://github.com/nlohmann/json/releases/tag/v3.1.1).

## v3.1.0 (2018-02-01)

Feature release. All changes are backward-compatible.

- Adds [UBJSON](../features/binary_formats/ubjson.md) read/write support and
  [JSON Merge Patch](../features/merge_patch.md) via [`merge_patch`](../api/basic_json/merge_patch.md).
- Switches to the Grisu2 algorithm for short, round-trippable floating-point output, and splits the
  header into [multiple files](../integration/index.md) with a forward-declaration header.

[Full release notes](https://github.com/nlohmann/json/releases/tag/v3.1.0).

## v3.0.1 (2017-12-29)

Fixes small issues in the [JSON Pointer](../features/json_pointer.md) and
[JSON Patch](../features/json_patch.md) implementations (invalid "copy" targets and non-integer array
indices). All changes are backward-compatible.
[Full release notes](https://github.com/nlohmann/json/releases/tag/v3.0.1).

## v3.0.0 (2017-12-17)

First 3.x release — a major release with breaking changes (see the
[migration guide](../integration/migration_guide.md)).

- Introduces user-defined [exceptions](exceptions.md) (`json::exception` and subtypes, each with an
  identifier).
- Adds a non-throwing [`accept`](../api/basic_json/accept.md) function and an `allow_exceptions` flag
  for [`parse`](../api/basic_json/parse.md), and an [`update`](../api/basic_json/update.md) function to
  merge objects.
- Adds streaming for CBOR and MessagePack and allows storing NaN/infinity.
- Non-UTF-8 strings now throw on serialization, and the iterator category changed to bidirectional.

[Full release notes](https://github.com/nlohmann/json/releases/tag/v3.0.0).

## v2.1.1 (2017-02-25)

Bug-fix release. All changes are backward-compatible.

- Makes number parsing and serialization locale-independent with correct floating-point
  round-tripping; released files are now GPG-signed.

[Full release notes](https://github.com/nlohmann/json/releases/tag/v2.1.1).

## v2.1.0 (2017-01-28)

Feature release. All changes are backward-compatible.

- Adds conversions from and to [arbitrary user-defined types](../features/arbitrary_types.md) via
  `to_json`/`from_json`, the [`meta`](../api/basic_json/meta.md) function, and the option to switch off
  exceptions ([`JSON_NOEXCEPTION`](../api/macros/json_noexception.md)).

[Full release notes](https://github.com/nlohmann/json/releases/tag/v2.1.0).

## v2.0.10 (2017-01-02)

Fixes several security-relevant bugs in the CBOR and MessagePack parsers found by OSS-Fuzz. All
changes are backward-compatible. [Full release notes](https://github.com/nlohmann/json/releases/tag/v2.0.10).

## v2.0.9 (2016-12-16)

Adds the [CBOR](../features/binary_formats/cbor.md) and
[MessagePack](../features/binary_formats/messagepack.md) binary formats. All changes are
backward-compatible. [Full release notes](https://github.com/nlohmann/json/releases/tag/v2.0.9).

## v2.0.8 (2016-12-02)

Adds the [`emplace`](../api/basic_json/emplace.md) and
[`emplace_back`](../api/basic_json/emplace_back.md) functions and improves parsing and serialization
performance. All changes are backward-compatible.
[Full release notes](https://github.com/nlohmann/json/releases/tag/v2.0.8).

## v2.0.7 (2016-11-02)

Fixes several parser bugs found through the "Parsing JSON is a Minefield" study (short files, encoding
detection, surrogate pairs). All changes are backward-compatible.
[Full release notes](https://github.com/nlohmann/json/releases/tag/v2.0.7).

## v2.0.6 (2016-10-15)

Fixes [`operator[]`](../api/basic_json/operator%5B%5D.md) for [JSON pointers](../features/json_pointer.md)
so that it creates missing values like the other overloads. All changes are backward-compatible.
[Full release notes](https://github.com/nlohmann/json/releases/tag/v2.0.6).

## v2.0.5 (2016-09-14)

Fixes a remaining stream end-of-file detection bug in the parser. All changes are backward-compatible.
[Full release notes](https://github.com/nlohmann/json/releases/tag/v2.0.5).

## v2.0.4 (2016-09-11)

Fixes stream end-of-file detection in the parser. All changes are backward-compatible.
[Full release notes](https://github.com/nlohmann/json/releases/tag/v2.0.4).

## v2.0.3 (2016-08-31)

Generalizes the parser to accept any contiguous sequence of one-byte elements and deprecates the
input-stream constructor in favor of the [`parse`](../api/basic_json/parse.md) function. All changes
are backward-compatible. [Full release notes](https://github.com/nlohmann/json/releases/tag/v2.0.3).

## v2.0.2 (2016-07-31)

Overhauls the parser (now rejecting unescaped control characters), tightens the class invariants, and
cleans up the code. All changes are backward-compatible.
[Full release notes](https://github.com/nlohmann/json/releases/tag/v2.0.2).

## v2.0.1 (2016-06-28)

Fixes a performance regression in the [`dump`](../api/basic_json/dump.md) function by adjusting the
stream locale once per serialization. All changes are backward-compatible.
[Full release notes](https://github.com/nlohmann/json/releases/tag/v2.0.1).

## v2.0.0 (2016-06-24)

Feature release with a minor (potentially non-backward-compatible) API change from added `noexcept`
and `constexpr` specifiers.

- Adds [JSON Pointer](../features/json_pointer.md) support in [`at`](../api/basic_json/at.md) and
  [`operator[]`](../api/basic_json/operator%5B%5D.md), plus [`flatten`](../api/basic_json/flatten.md)
  and [`unflatten`](../api/basic_json/unflatten.md).
- Adds [JSON Patch](../features/json_patch.md) via [`diff`](../api/basic_json/diff.md) and
  [`patch`](../api/basic_json/patch.md), unsigned 64-bit integer support, and locale-independent
  serialization.

[Full release notes](https://github.com/nlohmann/json/releases/tag/v2.0.0).

## v1.1.0 (2016-01-24)

Bug-fix and feature release. All changes are backward-compatible.

- Improves floating-point round-tripping, adds a `get_ref` accessor for stored values, and introduces
  runtime [assertions](../features/assertions.md).

[Full release notes](https://github.com/nlohmann/json/releases/tag/v1.1.0).

## v1.0.0 (2015-12-28)

First official release. [Full release notes](https://github.com/nlohmann/json/releases/tag/v1.0.0).

## See also

- [Migration Guide](../integration/migration_guide.md) — how to future-proof your code for the next
  major version and replace deprecated functions.

---

## File: docs/mkdocs/docs/home/sponsors.md

# Sponsors

You can sponsor this library at [GitHub Sponsors](https://github.com/sponsors/nlohmann).

## Priority Sponsor

- [Martti Laine](https://github.com/codeclown)
- [Paul Harrington](https://github.com/phrrngtn)

## Named Sponsors

- [Michael Hartmann](https://github.com/reFX-Mike)
- [Stefan Hagen](https://github.com/sthagen)
- [Steve Sperandeo](https://github.com/homer6)
- [Robert Jefe Lindstädt](https://github.com/eljefedelrodeodeljefe)
- [Steve Wagner](https://github.com/ciroque)
- [Lion Yang](https://github.com/LionNatsu)

Thanks everyone!