89 releases (38 breaking)

✓ Uses Rust 2018 edition

new 0.40.0 Aug 19, 2019
0.39.0 Jul 17, 2019
0.38.0 Mar 29, 2019
0.35.6 Dec 29, 2018
0.13.0 Jul 31, 2017

#3 in WebAssembly

Download history 3853/week @ 2019-05-06 3804/week @ 2019-05-13 4219/week @ 2019-05-20 4895/week @ 2019-05-27 6263/week @ 2019-06-03 5054/week @ 2019-06-10 4926/week @ 2019-06-17 5911/week @ 2019-06-24 6255/week @ 2019-07-01 5507/week @ 2019-07-08 4443/week @ 2019-07-15 4893/week @ 2019-07-22 5442/week @ 2019-07-29 6530/week @ 2019-08-05 5822/week @ 2019-08-12

22,899 downloads per month
Used in 42 crates (32 directly)




Low-level WebAssembly format library.

Build Status crates.io link


Rust WebAssembly format serializing/deserializing

Add to Cargo.toml

parity-wasm = "0.35"

and then

extern crate parity_wasm;

let module = parity_wasm::deserialize_file("./res/cases/v1/hello.wasm").unwrap();

let code_section = module.code_section().unwrap(); // Part of the module with functions code

println!("Function count in wasm file: {}", code_section.bodies().len());

Wabt Test suite

parity-wasm supports full wabt testsuite (https://github.com/WebAssembly/testsuite), running asserts that involves deserialization.

To run testsuite:

  • make sure you have all prerequisites to build wabt (since parity-wasm builds it internally using wabt-rs, see https://github.com/WebAssembly/wabt)
  • checkout with submodules (git submodule update --init --recursive)
  • run cargo test --release --manifest-path=spec/Cargo.toml

Decoder can be fuzzed with cargo-fuzz using wasm-opt (https://github.com/WebAssembly/binaryen):

  • make sure you have all prerequisites to build binaryen and cargo-fuzz (cmake and a C++11 toolchain)
  • checkout with submodules (git submodule update --init --recursive)
  • install cargo fuzz subcommand with cargo install cargo-fuzz
  • set rustup to use a nightly toolchain, because cargo fuzz uses a rust compiler plugin: rustup override set nightly
  • run cargo fuzz run deserialize

no_std crates

This crate has a feature, std, that is enabled by default. To use this crate in a no_std context, add the following to your Cargo.toml (still requires allocator though):

parity-wasm = { version = "0.35", default-features = false }

Until allocator api is stabilized, this type of use is limited to nightly Rust.


parity-wasm is primarily distributed under the terms of both the MIT license and the Apache License (Version 2.0), at your choice.

See LICENSE-APACHE, and LICENSE-MIT for details.


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

No runtime deps