92 releases (38 breaking)

✓ Uses Rust 2018 edition

0.40.3 Sep 29, 2019
0.40.1 Aug 26, 2019
0.39.0 Jul 17, 2019
0.38.0 Mar 29, 2019
0.13.0 Jul 31, 2017

#2 in WebAssembly

Download history 4724/week @ 2019-06-16 6018/week @ 2019-06-23 6344/week @ 2019-06-30 5233/week @ 2019-07-07 4695/week @ 2019-07-14 4851/week @ 2019-07-21 5502/week @ 2019-07-28 6422/week @ 2019-08-04 5823/week @ 2019-08-11 5299/week @ 2019-08-18 7446/week @ 2019-08-25 5895/week @ 2019-09-01 6740/week @ 2019-09-08 7523/week @ 2019-09-15 6815/week @ 2019-09-22

25,590 downloads per month
Used in 51 crates (33 directly)




Low-level WebAssembly format library.

Build Status crates.io link


Rust WebAssembly format serializing/deserializing

Add to Cargo.toml

parity-wasm = "0.40"

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 = "0.40", 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