WebAssembly is great as a target for a low-level code, but in order to do something useful, it needs to interact with the outer world. On the Web, this means performing all sorts of I/O through Web APIs, and here comes the challenge: they are designed to be asynchronous, but WebAssembly is not. Let's take a look at this problem and see how it can be fixed, as well as at some examples we can build by combining power of both modern Web APIs and a fast native compilation target.