A WebAssembly runtime first validates bytecode for well-typed control flow, declared imports, memory/table use, and structural correctness. Only validated code is compiled or interpreted.

  • Compilation may use an interpreter, a fast baseline compiler, an optimizing compiler, or ahead-of-time caching depending on the engine.
  • LLVM-based pipelines commonly compile C/C++/Rust into LLVM IR, optimize it, then lower it through a WASM backend.
  • WASM can beat JavaScript when predictable numeric types, compact binaries, and explicit memory layouts reduce runtime speculation.
  • JavaScript can still be faster for small, polymorphic, DOM-heavy, or boundary-call-heavy workloads.