Emscripten

Emscripten is an LLVM/Clang-based compiler that compiles C and C++ source code to WebAssembly, primarily for execution in web browsers.

Emscripten allows applications and libraries written in C or C++ to be compiled ahead of time and run efficiently in web browsers, typically at speeds comparable to or faster than interpreted or dynamically compiled JavaScript. It even emulates an entire POSIX operating system, enabling programmers to use functions from the C standard library (libc).

With the more recent development of the WebAssembly System Interface (WASI) and WebAssembly runtimes such as Node.js, Wasmtime, and Wasmer, Emscripten can also be used to compile to WebAssembly for execution in non-Web embeddings as well.