WebAssembly (WASM) is emerging as a universal compilation target, achieving 80-95% of native performance through a binary instruction format, static typing, and ahead-of-time compilation. Unlike JavaScript, WASM eliminates parsing overhead, provides predictable performance without JIT deoptimization, and supports SIMD operations. The linear memory model enables efficient data sharing between WASM and JavaScript. Real-world applications span image processing (Figma), games (Unity), and cryptography. Beyond browsers, WASI extends WASM to serverless computing with <1ms cold starts, far superior to containers. The Component Model and WIT (WebAssembly Interface Types) enable true language interoperability at the binary level. The ecosystem supports Rust, C/C++, Go, and more, with runtimes like Wasmtime and Wasmer. Current limitations include indirect DOM access and GC overhead, but proposals for native GC, exceptions, and threads are progressing. WASM represents a paradigm shift: a sandboxed, portable, high-performance execution environment that works across browsers, servers, edge, and embedded systems—truly becoming the assembly language of the internet age.