WebAssembly (Wasm) enables near-native performance in web browsers. It's a binary instruction format designed as a . Languages like C, C++, Rust, and Go can compile to WebAssembly. Wasm runs in a sandboxed environment with the same security model as JavaScript. Use cases include video editing, 3D gaming, image processing, and scientific computing. Emscripten compiles C/C++ code to WebAssembly for the web. Rust has excellent WebAssembly support through wasm-pack. WebAssembly cannot directly access the DOM; it communicates through JavaScript. Import objects bridge JavaScript functions into Wasm modules. Memory is shared between JavaScript and Wasm through linear memory. WebAssembly supports SIMD for parallel data processing. Threading enables multi-core processing through shared memory. Debugging tools include browser DevTools and source maps. Performance gains are significant for compute-intensive tasks. Bundle size of Wasm modules is typically larger than equivalent JavaScript. WebAssembly complements JavaScript rather than replacing it. Streaming compilation enables faster instantiation. WebAssembly is supported in all major browsers. It's particularly effective for porting existing native libraries to the web.