Wasmtime

Wasmtime is a standalone WebAssembly runtime designed to execute WebAssembly modules outside of web browsers. It is implemented in Rust and uses the Cranelift code generator to JIT-compile WebAssembly modules to native machine code. Wasmtime is developed as part of the Bytecode Alliance and originated as a project at Mozilla before being maintained by the alliance and community contributors. The runtime emphasizes safety, portability, and a small, embeddable footprint.

It provides comprehensive support for WebAssembly's System Interface (WASI), enabling modules to perform I/O, filesystem access, networking, and other system operations in a sandboxed environment. Wasmtime exposes an embedding API that allows host applications to instantiate and interact with WebAssembly modules, with bindings for Rust and other languages and a C API for broader language compatibility. In addition to its embedding API, Wasmtime ships with a command-line tool, also named wasmtime, which can run Wasm modules, configure WASI environments, and inspect modules at runtime.

Performance is achieved through JIT compilation with Cranelift, along with a compact, modular runtime design that supports features such as multi-module hosting, foreign function interfaces, and optional SIMD and bulk memory features when available in the module. Wasmtime aims to be portable across platforms including Linux, Windows, and macOS, and is used for server-side, edge, and embedded workloads that require safe execution of untrusted code.

Wasmtime is open-source under dual Apache-2.0 and MIT licenses.