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bytecodealliance/wasmtime

A standalone WebAssembly runtime built on the Cranelift code generator, with WASI support and embeddings for multiple languages.

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What is it?

Wasmtime is a standalone runtime for WebAssembly, the portable binary format for code that runs in browsers and outside them. It can run WebAssembly components from the command line with the wasmtime CLI, or be embedded into applications through its Rust crate and bindings for C, C++, Python, .NET, Go, and Ruby.

It compiles modules with the Cranelift code generator, either just-in-time at runtime or ahead of time. The project exposes configuration options for CPU and memory use, and provides WASI APIs so guest programs can interact with the host environment such as files and system resources. The project states that it passes the official WebAssembly test suite and implements the official wasm C API.

Wasmtime is maintained under the Bytecode Alliance and is written in Rust.

Key features

  • 01Compiles WebAssembly with the Cranelift code generator, either at runtime or ahead of time.
  • 02Provides WASI APIs for guest programs to access host resources.
  • 03Offers configuration controls for CPU and memory consumption.
  • 04Includes a CLI for running WebAssembly components directly.
  • 05Offers embedding bindings for Rust, C, C++, Python, .NET, Go, and Ruby.

Use cases

  • Running WebAssembly components from the command line.
  • Embedding a sandboxed WebAssembly runtime inside a Rust or C application.
  • Executing untrusted plugin code with WASI-based host access.

Quick start

  1. 1

    Install the Wasmtime CLI with the official install script or from the releases page

  2. 2

    Add the WebAssembly WASI target to Rust

    rustup target add wasm32-wasip2
  3. 3

    Compile a Rust hello-world program into a WebAssembly component

    rustc hello.rs --target wasm32-wasip2
  4. 4

    Run the compiled component with Wasmtime

    wasmtime hello.wasm

Things to know

  • The one-line install script is documented only for Linux and macOS; Windows users must use the releases page.

Topics

#webassembly#wasm#runtime#wasi#compiler#sandbox#rust#aot#cranelift#jit

FAQ

What is wasmtime?
A standalone WebAssembly runtime built on the Cranelift code generator, with WASI support and embeddings for multiple languages. Wasmtime is a standalone runtime for WebAssembly, the portable binary format for code that runs in browsers and outside them. It can run WebAssembly components from the command line with the wasmtime CLI, or be embedded into applications through its Rust crate and bindings for C, C++, Python, .NET, Go, and Ruby.
Is wasmtime free to use? What license does it have?
wasmtime is open source under the Apache-2.0 license. Check the license terms before using it in commercial products.
Is wasmtime still maintained?
Actively maintained. The last commit to wasmtime was on Oct 21, 2026.
What can I use wasmtime for?
Running WebAssembly components from the command line. Embedding a sandboxed WebAssembly runtime inside a Rust or C application. Executing untrusted plugin code with WASI-based host access.
How do I install wasmtime?
Install the Wasmtime CLI with the official install script or from the releases page Add the WebAssembly WASI target to Rust: rustup target add wasm32-wasip2 Compile a Rust hello-world program into a WebAssembly component: rustc hello.rs --target wasm32-wasip2 Run the compiled component with Wasmtime: wasmtime hello.wasm
Where can I get wasmtime?
The source code and installation instructions are on GitHub: https://github.com/bytecodealliance/wasmtime

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