> Unity uses the emscripten compiler toolchain to cross-compile the Unity runtime code (written in C and C++) into WebAssembly (also known as Wasm). It is designed to be small in size, load-time and memory efficient as well as able to deliver close to native speed execution.

>For more information about WebAssembly in Unity, check this blog post.

>To convert the .NET game code (your C# scripts) into WebAssembly, we use a technology called IL2CPP. IL2CPP takes .NET bytecode and converts it to corresponding C++ source files, which is then compiled using emscripten to convert your scripts to Wasm.

>Emscripten は LLVM を利用した wasm 出力のためのツールチェーンで、標準 C ライブラリのみならず、OpenGL や pthreads などの変換も対応してくれているので、既存プロジェクトの wasm への出力に関してはものすごく強力なツールです。