Skip to content
This repository has been archived by the owner. It is now read-only.
Switch branches/tags

Latest commit


Git stats


Failed to load latest commit information.
Latest commit message
Commit time


A Bytecode Alliance project

A Rust toolkit for working with WebAssembly Interface Types.

Note: This repository is now archived. The interface types proposal has changed quite a lot since this was first implemented and the trajectory of the proposal and the implementation within wasmtime no longer aligns with this repository.


This project is a work-in-progress. The official proposal itself has neither an official text specification nor an official binary specification. Instability and breaking changes should be expected from this project.

This is attempting to fill functionality gaps in the proposal to ensure that toolchains can be developed for wasm interface types to help provide feedback on the proposal and also provide a testing ground for ideas to be concretely gamed out.

Functionality provided by this project currently is:

  • wat2wasm - a converter from a textual format of wasm interface types to a binary *.wasm module, including support for wasm interface types

  • wasm2wat - same as above, but the other way around. Takes a *.wasm module and prints out the *.wat file, including interface types annotations if there are any.

  • crates/text - a Rust library which parses the text format for wasm interface types

  • crates/parser - a Rust library which parses the binary format for wasm interface types

  • crates/writer - a Rust library which is a raw interface for writing the binary format of wasm interface types

  • crates/validator - a Rust library which performs validation over a wasm module which contains wasm interface types, specifically focusing on the wasm interface types section.

  • crates/printer - a Rust library which will print the binary representation of a wasm interface types *.wasm blob into its textual format.

  • crates/walrus - an implementation of a custom section type for the walrus Rust crate, useful for more advanced transformation on interface type sections.

The current state of the binary encoding as well as some semantic nodes are located in as well as To reiterate though, this is not an official specification and the official specification is in flux, use these tools appropriately!


The top-level tests directory contains a number of *.wat files which are intended to be various forms of tests for the wasm interface types proposal. They're annotated at the top with things like ;; parse-fail or ;; validate-fail if they're expected to be invalid, otherwise the comment at the bottom is the round-trip representation through the tooling here (text -> binary -> printing).


This project is licensed under the Apache 2.0 license with the LLVM exception. See LICENSE for more details.


Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in this project by you, as defined in the Apache-2.0 license, shall be licensed as above, without any additional terms or conditions.


Raw Rust toolchain support for Wasm Interface Types



Code of conduct





No releases published


No packages published