WebAssembly (Wasm) is a low-level assembly-like language that brings near-native performance to the web. It serves as a compilation target for languages like C/C++, C#, and Rust, allowing high-performance code to run directly in the browser.

WebAssembly is designed to complement and run alongside JavaScript. Using the WebAssembly JavaScript APIs, you can load WebAssembly modules into a JavaScript app and share functionality between the two. This allows you to take advantage of WebAssembly's performance and power and JavaScript's expressiveness and flexibility in the same app — without having to write low-level WebAssembly code yourself.

Guides

The WebAssembly guides cover topics such as high-level concepts, compiling from different languages, the textual representation of the Wasm binary format, and how to run WebAssembly.

API reference

The WebAssembly reference is split into the following sections:

WebAssembly JavaScript API

The WebAssembly JavaScript object acts as the namespace for all WebAssembly-related functionality.

WebAssembly value types

The different WebAssembly value types.

WebAssembly definitions

The top-level definitions available in Wasm for defining module features such as tables, types, memories, functions, etc.

WebAssembly instructions

The instructions available in Wasm for handling logic.

Examples

Our reference documentation has several live examples to demonstrate how the different features work. You can find additional examples in our webassembly-examples repo.

See also

• webassembly.org
• WebAssembly browser feature support status on webassembly.org (2026)
• W3C WebAssembly Community Group