owasm-utils 0.6.0

Collection of command-line utilities and corresponding Rust api for producing owasm-compatible executables


Build Status

Collection of WASM utilities used in Parity and WASM contract development

Build tools for cargo

Easiest way to use is to install via cargo install:

cargo install owasm-utils-cli --bin wasm-build

Symbols pruning (wasm-prune)

cargo install owasm-utils-cli --bin wasm-prune
wasm-prune <input_wasm_binary.wasm> <output_wasm_binary.wasm>

This will optimize WASM symbols tree to leave only those elements that are used by contract call function entry.

Gas counter (wasm-gas)

For development puposes, raw WASM contract can be injected with gas counters (the same way as it done by Parity runtime when running contracts)

cargo install owasm-utils-cli --bin wasm-gas
wasm-gas <input_wasm_binary.wasm> <output_wasm_binary.wasm>

Externalization (wasm-ext)

Parity WASM runtime provides some library functions that can be commonly found in libc. WASM binary size can be reduced and performance may be improved if these functions are used. This utility scans for invocations of the following functions inside the WASM binary:

  • _malloc,
  • _free,
  • _memcpy,
  • _memset,
  • _memmove

And then substitutes them with invocations of the imported ones. Should be run before wasm-opt for better results.

cargo install owasm-utils-cli --bin wasm-ext
wasm-ext <input_wasm_binary.wasm> <output_wasm_binary.wasm>


All executables use corresponding api methods of the root crate and can be combined in other build tools.


wasm-utils 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 wasm-utils by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.