WIT (WebAssembly Interface Types)

WIT is the Interface Definition Language (IDL) for the WebAssembly Component Model. It defines typed contracts between components in a language-agnostic way, enabling interoperability across programming languages at the wasm boundary.

See also: wasmtime skill for runtime embedding and compilation details.

When to Use This Skill

Activate when:

• Writing .wit files to define component interfaces
• Designing worlds for WebAssembly components
• Understanding the Component Model type system
• Using cargo-component, wit-bindgen, or wasm-tools
• Mapping WIT types to host language types (Rust, Go, Python, JavaScript)
• Structuring packages and namespaces for wasm components
• Composing components via shared interfaces

WIT File Structure