The video below demonstrates the basic functions of the WebAssembly Explorer, which lets developers type in simple C or C++ programs and compile them to WebAssembly.
While the WebAssembly Explorer is a great learning tool, it’s still in early development and not yet suitable for complex programs. Developers who need a production-grade compiler suite should look to Emscripten, which was originally written to output asm.js but has now been extended to produce WebAssembly as well.
You can find the WebAssembly Explorer’s source code on GitHub, and you can begin experimenting with WebAssembly when it lands in Firefox 52 later this week.
Source: Mozilla Hacks Previewing the WebAssembly Explorer