webidl2wit - WebIDL to wit converter

May 13, 2026 · View on GitHub

Warning

This project is a Work In Progress ("WIP")

This project converts WebIDL to WebAssembly Interface Types ("WIT"), enabling WebAssembly components to interact with interfaces (most importantly browser primitives) defined via WebIDL.

Usage

webidl2wit can be used as a library from your project:

webidl2wit = "0.1.0"

webidl2wit can also be used as a CLI, via the workspace member project webidl2wit-cli:

cargo install webidl2wit-cli

Type conversions

This section lists the type conversions between WebIDL and WIT, as implemented by webidl2wit:

WebIDL type	wit type
`any`	❓
`undefined`	just leave it out
`boolean`	`bool`
`byte`	`s8`
`octet`	`u8`
`short`	`s16`
`unsigned short`	`u16`
`long`	`s32`
`unsigned long`	`u32`
`long long`	`s64`
`unsigned long long`	`u64`
`float`	`f32`
`unrestricted float`	`f32`
`double`	`f64`
`unrestricted double`	`f64`
`bigint`	❓
`DOMString`	`string`
`ByteString`	`string`
`USVString`	`string`
`object`	❓
`symbol`	❓
`interface`	`resource` or `interface`
`callback interface`	❓
`dictionary`	`record`
`enum`	`enum`
`callback`	`func`
`constructor`	`constructor`
`T?` (optional)	`option<T>`
`sequence<T>`	`list<T>`
`record<K, V>`	A custom resource
`Promise<T>`	`future<T>`
`or` (union)	`variant`
Buffer types (e.g. `Int8Array`)	A custom resource
`FrozenArray<T>`	`list<T>`
`ObservableArray<T>`	❓
`setlike<T>`	Add set methods
`maplike<K, V>`	`map<K, V>`
`namespace`	`resource` or `interface`
`typedef`	`type`
`const`	A getter
`EventHandler`	`stream`

❓ = Not yet sure how to deal with this type.