Emscripten is a toolchain for compiling to asm.js and WebAssembly, built using
LLVM, that lets you run C and C++ on the web at near-native speed without
plugins.

Emscripten compiles C and C++ to WebAssembly using LLVM and Binaryen Emscripten
output can run on the Web, in Node.js, and in wasm runtimes

Emscripten provides Web support for popular portable APIs such as OpenGL and
SDL2, allowing complex graphical native applications to be ported, such as the
Unity game engine.