Web Assembly (WASM)
By W3C
WebAssembly (WASM) is a low-level, binary instruction format that runs in the browser at near-native speed, letting languages like C, C++, Rust, and Go execute performance-critical code on the web alongside JavaScript.
Definition
WebAssembly (WASM) is a low-level, binary instruction format that runs in the browser at near-native speed, letting languages like C, C++, Rust, and Go execute performance-critical code on the web alongside JavaScript.
Overview
WebAssembly emerged from a W3C-backed collaboration between major browser vendors, reaching a stable 1.0 specification supported across all major browsers around 2017. Rather than replacing JavaScript, WASM was designed as a compilation target that runs alongside it: developers write performance-sensitive code in a language like Rust, C++, or Go, compile it to a compact `.wasm` binary, and load it into a web page where it executes at speeds close to native machine code, communicating with JavaScript through a defined interface. This makes previously web-impractical workloads feasible in the browser — video and image editing, CAD tools, games, scientific computing, and cryptography libraries can run client-side with performance JavaScript alone couldn't reliably deliver. Notable production examples include Figma's design engine, AutoCAD's web version, and Google Earth's browser edition, all of which rely on WASM for their core rendering or computation. Beyond the browser, WebAssembly's sandboxed, portable execution model has expanded into server-side and edge computing use cases — platforms run WASM modules as lightweight, fast-starting alternatives to containers for Edge Functions — extending WASM's relevance well past its original in-browser use case. Runtimes like Docker and languages such as Rust and C++ are commonly compiled to WebAssembly for near-native performance in the browser.
Key Concepts
- Binary instruction format executing at near-native speed in the browser
- Compilation target for languages like Rust, C++, C, and Go
- Runs alongside JavaScript, communicating through a defined interface
- Sandboxed execution model for security
- Supported natively across all major modern browsers
- Expanding use in server-side and edge computing beyond the browser