What is WebAssembly (Wasm)?
A portable binary instruction format that runs near-native-speed code from languages like Rust and C++ in the browser.
Definition
WebAssembly is a stack-based virtual machine and binary format, standardized by the W3C, that browsers execute alongside JavaScript in the same sandbox. Code written in Rust, C/C++, Go, or C# (via Emscripten, wasm-pack, or Blazor) compiles to compact .wasm modules with predictable, near-native performance—powering Figma's rendering engine, Google Earth, ffmpeg.wasm, and SQLite in the browser. Wasm modules interoperate with JavaScript through imports/exports, with heavy data passed via linear memory. Beyond browsers, WASI extends Wasm to servers and edge runtimes (Fastly, Cloudflare, wasmtime), positioning it as a lightweight, sandboxed alternative to containers.