Wasmtime: a WebAssembly Runtime

A Bytecode Alliance project

Wasmtime is a standalone wasm-only optimizing runtime for WebAssembly and WASI. It 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.

To get started, visit wasmtime.dev.

There are Rust, C, and C++ toolchains that can compile programs with WASI. See the WASI intro for more information, and the WASI tutorial for a tutorial on compiling and running programs using WASI and wasmtime, as well as an overview of the filesystem sandboxing system.

Wasmtime passes the WebAssembly spec testsuite. To run it, update the tests/spec_testsuite submodule with git submodule update --remote, and it will be run as part of cargo test.

Wasmtime does not yet implement Spectre mitigations, however this is a subject of ongoing research.

Additional goals for Wasmtime include:

• Support a variety of host APIs (not just WASI), with fast calling sequences, and develop proposals for additional API modules to be part of WASI.
• Facilitate development and testing around the Cranelift and Lightbeam JITs, and other WebAssembly execution strategies.
• Develop a native ABI used for compiling WebAssembly suitable for use in both JIT and AOT to native object files.

Including Wasmtime in your project

Wasmtime exposes an API for embedding as a library through the wasmtime subcrate, which contains both a high-level and safe Rust API, as well as a C-compatible API compatible with the proposed WebAssembly C API.

For more information, see the Rust API embedding chapter of the Wasmtime documentation.

It's Wasmtime.