32 releases (breaking)

Uses new Rust 2021

new 0.37.0 May 20, 2022
0.35.3 Apr 11, 2022
0.35.2 Mar 31, 2022
0.32.0 Dec 13, 2021
0.15.0 Mar 31, 2020

#555 in WebAssembly

Download history 2056/week @ 2022-01-28 4022/week @ 2022-02-04 4134/week @ 2022-02-11 4788/week @ 2022-02-18 2326/week @ 2022-02-25 3565/week @ 2022-03-04 4154/week @ 2022-03-11 3406/week @ 2022-03-18 7004/week @ 2022-03-25 8746/week @ 2022-04-01 8232/week @ 2022-04-08 5444/week @ 2022-04-15 9682/week @ 2022-04-22 6227/week @ 2022-04-29 6611/week @ 2022-05-06 7390/week @ 2022-05-13

31,731 downloads per month
Used in 41 crates (via wiggle)

Apache-2.0 WITH LLVM-exception



A standalone runtime for WebAssembly

A Bytecode Alliance project

build status zulip chat supported rustc stable Documentation Status

Guide | Contributing | Website | Chat


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

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

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


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

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

and compile/run it with:

$ rustup target add wasm32-wasi
$ rustc hello.rs --target wasm32-wasi
$ wasmtime hello.wasm
Hello, world!


  • Lightweight. Wasmtime is a standalone runtime for WebAssembly that scales with your needs. It fits on tiny chips as well as makes use of huge servers. Wasmtime can be embedded into almost any application too.

  • Fast. Wasmtime is built on the optimizing Cranelift code generator to quickly generate high-quality machine code at runtime.

  • Configurable. Whether you need to precompile your wasm ahead of time, or interpret it at runtime, Wasmtime has you covered for all your wasm-executing needs.

  • 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

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


📚 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.


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