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What is WebAssembly?

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Quick answer

WebAssembly (Wasm) is a fast, low-level binary format that runs in web browsers at near-native speed. It lets code written in languages like C++, Rust, and Go run on a web page alongside JavaScript, powering games, video editors, and CAD tools in the browser.

Key things to understand

  1. A compact binary instruction format browsers execute far faster than they parse JavaScript.
  2. Languages like Rust, C, C++, and Go compile to Wasm and run on any modern browser.
  3. It runs in the same secure sandbox as JavaScript and works with it rather than replacing it.
  4. Now used outside browsers too (servers, edge, plugins) via the WebAssembly System Interface (WASI).

People also ask

Does WebAssembly replace JavaScript?
No. It complements JavaScript for heavy work; most apps use both, with JavaScript running the page and Wasm handling heavy computation.
Is WebAssembly safe?
Yes — it runs in the browser's sandbox with the same restrictions as JavaScript, so it can't freely access your files or system.
What can you build with WebAssembly?
Browser games, photo and video editors, 3D and CAD tools, emulators, and ports of desktop apps like Figma and AutoCAD.