There is only one file type that uses the .WASM extension:
WebAssembly Binary File
You can compile C, C++, and Rust languages into the WebAssembly binary format (WASM file) using various programs, such as Emscripten and WebAssembly Explorer.
WebAssembly is useful because it is efficient, fast, safe, and can be debugged and tested. The format also allows you to integrate open source projects written in C, C++, and Rust into webpages and apps.
Updated: December 10, 2018