emcc

Compile C to WebAssembly

$ emcc [input.c] -o [output.wasm]

$ emcc [input.c] -o [output.js]

$ emcc [input.c] -o [output.html]

$ em++ [input.cpp] -o [output.js]

$ emcc -Os [input.c] -o [output.wasm]

$ emcc -O3 [input.c] -o [output.wasm]

$ emcc -sEXPORTED_FUNCTIONS=['_main','_myFunc'] [input.c] -o [output.js]

emcc [options] files

emcc (Emscripten Compiler Frontend) compiles C and C++ code to WebAssembly (Wasm) or JavaScript using LLVM and Emscripten. It enables running native code in web browsers and other Wasm runtimes.
Emscripten provides a compatibility layer for POSIX APIs, OpenGL (via WebGL), and SDL. It can compile entire codebases including games and applications to run in browsers.

-o file

Output file (.js, .wasm, .html).

Optimization levels.

Emscripten-specific settings.

Include directory.

Library directory.

Link library.

Generate debug information.

Preload file into virtual filesystem.

Embed file in output.

Output as ES6 module.

Not all C/C++ features work identically. File system access requires virtual filesystem. Threading needs SharedArrayBuffer. Performance differs from native. Large applications may have long compile times. Browser security restrictions apply.

Emscripten was created by Alon Zakai at Mozilla in 2011, initially targeting asm.js before WebAssembly existed. When WebAssembly launched in 2017, Emscripten became the primary compiler toolchain for bringing C/C++ to the web.

clang(1), wasm-ld(1), wasm2wat(1)