An implementation of the binary format section from the Webassembly spec.

parser, binary-format, nom



An implementation of the Webassembly spec in Rust.

The structure of the project tries to follow the structure of the Spec where possible. Current progress:

  • Stucture (crate greenwasm-structure): Typedefs for Wasm Types, Instructions and Modules.
  • Validation (crate greenwasm-validation): Validator for a Wasm Module.
  • Execution (crate greenwasm-execution): Naive Execution Engine for a Wasm Module.
  • Binary-Format (crate greenwasm-binary-format) parser for the .wasm binary format.
  • Text-Format: Parser for the .wat text format.

The individual crates are reexported from the central greenwasm crate, which also ties them together with a testsuite and some fuzzer scripts.

In the current version this is mainly a learning exercise, but the long-term goals include:

  • Modularity: It should be possible to use the parser/validator/typedefs independent from each other. This is already somewhat possible due to the split in different crates.
  • Genericy: It should be possible to parse/validate independent from the underlying AST format.
  • Performance: It should be usable for performance-oriented projects.


The greenwasm-spectest crate contains a library shim around a mirror of the official Webasembly MVP testsuite.

It is used as a dev-dependency by the main greenwasm crate, but has no dependencies on other crates in this repo. As such, it can be used as a independent testsuite launcher for other Webassembly implementations.


Licensed under either of

at your option.


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