Wasmtime

A fast and secure runtime for WebAssembly

ABytecode Alliance project

Install

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

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

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

Example

If you've got theRust compilerinstalled then you can take some Rustsource code:

fnmain() {    println!("Hello, world!");}

and compile/run it with:

$ rustup target add wasm32-wasip1$ rustc hello.rs --target wasm32-wasip1$ wasmtime hello.wasmHello, world!

Features

• Fast. Wasmtime is built on the optimizingCranelift code generator toquickly generate high-quality machine code either at runtime orahead-of-time. Wasmtime is optimized for efficient instantiation, low-overheadcalls between the embedder and wasm, and scalability of concurrent instances.

• Secure. Wasmtime's development is strongly focused on correctness andsecurity. Building on top of Rust's runtime safety guarantees, each Wasmtimefeature goes through careful review and consideration via anRFCprocess. Once features are designed and implemented, they undergo 24/7fuzzing donated byGoogle's OSS Fuzz. As features stabilize they become partof arelease, and when things go wrong we have awell-definedsecurity policy in place to quickly mitigate and patch anyissues. We follow best practices for defense-in-depth and integrateprotections and mitigations for issues like Spectre. Finally, we're working topush the state-of-the-art by collaborating with academic researchers toformally verify critical parts of Wasmtime and Cranelift.

• Configurable. Wasmtime uses sensible defaults, but can also beconfigured to provide more fine-grained control over things like CPU andmemory consumption. Whether you want to run Wasmtime in a tiny environment oron massive servers with many concurrent instances, we've got you covered.

• WASI. Wasmtime supports a rich set of APIs for interacting with the hostenvironment through theWASI standard.

• Standards Compliant. Wasmtime passes theofficial WebAssembly testsuite, implements theofficial CAPI of wasm, and implementsfuture proposals to WebAssembly aswell. Wasmtime developers are intimately engaged with the WebAssemblystandards process all along the way too.

Language Support

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

• Rust - thewasmtime crate
• C - thewasm.h,wasi.h, andwasmtime.h headers,CMake orwasmtime Conan package
• C++ - thewasmtime-cpp repository or usewasmtime-cpp Conan package
• Python - thewasmtime PyPI package
• .NET - theWasmtime NuGet package
• Go - thewasmtime-go repository
• Ruby - thewasmtime gem

Documentation

Thewasmtime guide is the best starting point to learn about whatWasmtime can do for you or help answer your questions about Wasmtime. If you'reinterested in contributing to Wasmtime,it can also help you dothat!