wasmtime

A lightweight WebAssembly runtime that is fast, secure, and standards-compliant

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README.md

<div align="center">
<h1><code>wasmtime</code></h1>

<p>
<strong>A standalone runtime for
<a href="https://webassembly.org/">WebAssembly</a></strong>
</p>

<strong>A <a href="https://bytecodealliance.org/">Bytecode Alliance</a> project</strong>

<p>
<a href="https://github.com/bytecodealliance/wasmtime/actions?query=workflow%3ACI"><img src="https://github.com/bytecodealliance/wasmtime/workflows/CI/badge.svg" alt="build status" /></a>
<a href="https://bytecodealliance.zulipchat.com/#narrow/stream/217126-wasmtime"><img src="https://img.shields.io/badge/zulip-join_chat-brightgreen.svg" alt="zulip chat" /></a>
<img src="https://img.shields.io/badge/rustc-stable+-green.svg" alt="supported rustc stable" />
<a href="https://docs.rs/wasmtime"><img src="https://docs.rs/wasmtime/badge.svg" alt="Documentation Status" /></a>
</p>

<h3>
<a href="https://bytecodealliance.github.io/wasmtime/">Guide</a>
<span> | </span>
<a href="https://bytecodealliance.github.io/wasmtime/contributing.html">Contributing</a>
<span> | </span>
<a href="https://wasmtime.dev/">Website</a>
<span> | </span>
<a href="https://bytecodealliance.zulipchat.com/#narrow/stream/217126-wasmtime">Chat</a>
</h3>
</div>

Installation

The Wasmtime CLI can be installed on Linux and macOS (locally) with a small install
script:

console
curl https://wasmtime.dev/install.sh -sSf | bash

This script installs into $WASMTIME_HOME (defaults to $HOME/.wasmtime), and executable is placed in $WASMTIME_HOME/bin.

After running the install script above, follow the on-screen instructions.

Windows or otherwise interested users can download installers and
binaries directly from the GitHub
Releases page.

For additional installation options, refer to the online book CLI installation page.

Documentation on Wasmtime's currently supported versions can be found in the
online book
documentation.

Example

If you've got the Rust compiler
installed then you can take some Rust
source code:

rust
fn main() {
    println!("Hello, world!");
}

and compile it into a WebAssembly component with:

console
rustup target add wasm32-wasip2
rustc hello.rs --target wasm32-wasip2

Once compiled, you can run your component:

console
wasmtime hello.wasm

You should see the following output:

text
Hello, world!

(Note: make sure you installed Rust using the [rustup][rustup] method in the official
instructions above, and do not have a copy of the Rust toolchain installed on
your system in some other way as well (e.g. the system package manager). Otherwise, the rustup target add...
command may not install the target for the correct copy of Rust.)

[rustup]: https://rustup.rs

Features

* Fast. Wasmtime is built on the optimizing [Cranelift] code generator to
quickly generate high-quality machine code either at runtime or
ahead-of-time. Wasmtime is optimized for efficient instantiation, low-overhead
calls between the embedder and wasm, and scalability of concurrent instances.

* [Secure]. Wasmtime's development is strongly focused on correctness and
security. Building on top of Rust's runtime safety guarantees, each Wasmtime
feature goes through careful review and consideration via an [RFC
process]. Once features are designed and implemented, they undergo 24/7
fuzzing donated by [Google's OSS Fuzz]. As features stabilize they become part
of a [release][release policy], and when things go wrong we have a
well-defined [security policy] in place to quickly mitigate and patch any
issues. We follow best practices for defense-in-depth and integrate
protections and mitigations for issues like Spectre. Finally, we're working to
push the state-of-the-art by collaborating with academic researchers to
formally verify critical parts of Wasmtime and Cranelift.

* [Configurable]. Wasmtime uses sensible defaults, but can also be
configured to provide more fine-grained control over things like CPU and
memory consumption. Whether you want to run Wasmtime in a tiny environment or
on massive servers with many concurrent instances, we've got you covered.

* [WASI]. Wasmtime supports a rich set of APIs for interacting with the host
environment through the WASI standard.

* [Standards Compliant]. Wasmtime passes the official WebAssembly test
suite, implements the official C
API of wasm, and implements
future proposals to WebAssembly as
well. Wasmtime developers are intimately engaged with the WebAssembly
standards process all along the way too.

[Wasmtime]: https://github.com/bytecodealliance/wasmtime
[Cranelift]: https://cranelift.dev/
[Google's OSS Fuzz]: https://google.github.io/oss-fuzz/
[security policy]: https://bytecodealliance.org/security
[RFC process]: https://github.com/bytecodealliance/rfcs
[release policy]: https://docs.wasmtime.dev/stability-release.html
[Secure]: https://docs.wasmtime.dev/security.html
[Configurable]: https://docs.rs/wasmtime/latest/wasmtime/struct.Config.html
[WASI]: https://docs.rs/wasmtime-wasi/latest/wasmtime_wasi/
[Standards Compliant]: https://docs.wasmtime.dev/stability-tiers.html

Language Support

You can use Wasmtime from a variety of different languages through embeddings of
the implementation.

Languages supported by the Bytecode Alliance:

* [Rust] - the [wasmtime crate]
* [C] - the [wasm.h, wasi.h, and wasmtime.h headers][c-headers], CMake
* C++ - the [wasmtime.hh header][c-headers]
* [Python] - the [wasmtime PyPI package]
* [.NET] - the [Wasmtime NuGet package]
* [Go] - the [wasmtime-go repository]
* [Ruby] - the [wasmtime gem]

Languages supported by the community:

* [Elixir] - the [wasmex hex package]
* Perl - the [Wasm Perl package's Wasm::Wasmtime]

[Rust]: https://bytecodealliance.github.io/wasmtime/lang-rust.html
[C]: https://bytecodealliance.github.io/wasmtime/lang-c.html
[wasmtime crate]: https://crates.io/crates/wasmtime
[c-headers]: https://bytecodealliance.github.io/wasmtime/c-api/
[Python]: https://bytecodealliance.github.io/wasmtime/lang-python.html
[wasmtime PyPI package]: https://pypi.org/project/wasmtime/
[.NET]: https://bytecodealliance.github.io/wasmtime/lang-dotnet.html
[Wasmtime NuGet package]: https://www.nuget.org/packages/Wasmtime
[Go]: https://bytecodealliance.github.io/wasmtime/lang-go.html
[wasmtime-go repository]: https://pkg.go.dev/github.com/bytecodealliance/wasmtime-go
[Ruby]: https://bytecodealliance.github.io/wasmtime/lang-ruby.html
[wasmtime gem]: https://rubygems.org/gems/wasmtime
[Elixir]: https://docs.wasmtime.dev/lang-elixir.html
[wasmex hex package]: https://hex.pm/packages/wasmex
[Wasm Perl package's Wasm::Wasmtime]: https://metacpan.org/pod/Wasm::Wasmtime

Documentation

[📚 Read the Wasmtime guide here! 📚][guide]

The [wasmtime guide][guide] is the best starting point to learn about what
Wasmtime can do for you or help answer your questions about Wasmtime. If you're
curious in contributing to Wasmtime, [it can also help you do
that][contributing]!

[contributing]: https://bytecodealliance.github.io/wasmtime/contributing.html
[guide]: https://bytecodealliance.github.io/wasmtime

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It's Wasmtime.