wasmtime Documentation

File: README.md Copy Chapter

Installation Copy Chapter

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

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 Copy Chapter

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

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

and compile it into a WebAssembly component with:

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

Once compiled, you can run your component:

wasmtime hello.wasm

You should see the following output:

Hello, world!

(Note: make sure you installed Rust using the 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.)

Features Copy Chapter

• 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, 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.

Language Support Copy Chapter

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, CMake
• C++ - the wasmtime.hh header
• 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

Documentation Copy Chapter

📚 Read the Wasmtime guide here! 📚

The wasmtime 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!

It's Wasmtime.

File: docs/introduction.md Copy Chapter

Introduction

Wasmtime is a standalone runtime for WebAssembly, WASI, and the
Component Model by the Bytecode Alliance.

WebAssembly (abbreviated Wasm) is a binary instruction format that is designed
to be a portable compilation target for programming languages. Wasm binaries
typically have a .wasm file extension. In this documentation, we'll also use
the textual representation of the binary files, which have a .wat file
extension.

WASI (the WebAssembly System Interface) defines interfaces that provide a
secure and portable way to access several operating-system-like features such as
filesystems, networking, clocks, and random numbers.

The Component Model is a Wasm architecture that provides a binary format for
portable, cross-language composition. More specifically, it supports the use of
interfaces via which components can communicate with each other. WASI
is defined in terms of component model interfaces.

Wasmtime runs WebAssembly code outside of the Web, and can be used both as a
command-line utility or as a library embedded in a larger application. It
strives to be

• Fast: Wasmtime is built on the optimizing Cranelift code generator.
• Secure: Wasmtime's development is strongly focused on correctness and
  security.
• Configurable: Wasmtime uses sensible defaults, but can also be configured
  to provide more fine-grained control over things like CPU and memory
  consumption.
• Standards Compliant: Wasmtime passes the official WebAssembly test suite
  and the Wasmtime developers are intimately engaged with the WebAssembly
  standards process.

This documentation is intended to serve a number of purposes and within you'll
find:

• How to use Wasmtime from a number of languages
• How to install and use the wasmtime CLI
• Information about stability and security in
  Wasmtime.
• Documentation about contributing to Wasmtime.

... and more! The source for this guide lives on
GitHub and
contributions are welcome!