74 releases (30 breaking)

0.32.0 Aug 28, 2018
0.31.1 Jul 17, 2018
0.27.5 Mar 25, 2018
0.19.0 Dec 28, 2017
0.13.0 Jul 31, 2017

#1 in WebAssembly

Download history 2591/week @ 2018-09-17 3387/week @ 2018-09-24 3215/week @ 2018-10-01 2705/week @ 2018-10-08 3031/week @ 2018-10-15 2848/week @ 2018-10-22 2805/week @ 2018-10-29 2683/week @ 2018-11-05 3013/week @ 2018-11-12 3244/week @ 2018-11-19 2725/week @ 2018-11-26 3869/week @ 2018-12-03 2597/week @ 2018-12-10

17,369 downloads per month
Used in 34 crates (27 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.