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0.2.92 Mar 4, 2024
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0.2.89 Nov 27, 2023
0.2.87 Jun 12, 2023
0.2.67 Jul 28, 2020

#1367 in WebAssembly

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181,525 downloads per month
Used in 32 crates (via wasm-bindgen-cli-support)


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Facilitating high-level interactions between Wasm modules and JavaScript.

Build Status Crates.io version Download docs.rs docs

Guide (main branch) | API Docs | Contributing | Chat

Built with 🦀🕸 by The Rust and WebAssembly Working Group

Install wasm-bindgen-cli

You can install it using cargo install:

cargo install wasm-bindgen-cli

Or, you can download it from the release page.

If you have cargo-binstall installed, then you can install the pre-built artifacts by running:

cargo binstall wasm-bindgen-cli


Import JavaScript things into Rust and export Rust things to JavaScript.

use wasm_bindgen::prelude::*;

// Import the `window.alert` function from the Web.
extern "C" {
    fn alert(s: &str);

// Export a `greet` function from Rust to JavaScript, that alerts a
// hello message.
pub fn greet(name: &str) {
    alert(&format!("Hello, {}!", name));

Use exported Rust things from JavaScript with ECMAScript modules!

import { greet } from "./hello_world";



  • Lightweight. Only pay for what you use. wasm-bindgen only generates bindings and glue for the JavaScript imports you actually use and Rust functionality that you export. For example, importing and using the document.querySelector method doesn't cause Node.prototype.appendChild or window.alert to be included in the bindings as well.

  • ECMAScript modules. Just import WebAssembly modules the same way you would import JavaScript modules. Future compatible with WebAssembly modules and ECMAScript modules integration.

  • Designed with the "Web IDL bindings" proposal in mind. Eventually, there won't be any JavaScript shims between Rust-generated wasm functions and native DOM methods. Because the wasm functions are statically type checked, some of those native methods' dynamic type checks should become unnecessary, promising to unlock even-faster-than-JavaScript DOM access.


📚 Read the wasm-bindgen guide here! 📚

You can find general documentation about using Rust and WebAssembly together here.

API Docs


This project is licensed under either of

at your option.


See the "Contributing" section of the guide for information on hacking on wasm-bindgen!

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


Transformation for wasm-bindgen to enable usage of externref in a wasm module.

This crate is in charge of enabling code using wasm-bindgen to use the externref type inside of the wasm module. This transformation pass primarily wraps exports and imports in shims which use externref, but quickly turn them into i32 value types. This is all largely a stopgap until Rust has first-class support for the externref type, but that's thought to be in the far future and will take quite some time to implement. In the meantime, we have this!

The pass here works by collecting information during binding generation about imports and exports. Afterwards this pass runs in one go against a wasm module, updating exports, imports, calls to these functions, etc. The goal at least is to have valid wasm modules coming in that don't use externref and valid wasm modules going out which use externref at the fringes.


~122K SLoC