WebAssembly was initially created as a sandbox for the Web. It was designed to be lightweight, portable and compatible with most programming languages. Given these characteristics, it's no surprise that a lot of people are starting to take it outside the browser and into the realm of desktop and cloud applications. In this talk I'll discuss why WebAssembly is perfectly suited as a runtime for serverless functions. I'll discuss how WebAssembly can be used to build serverless functions, how it compares with Docker and other runtimes and how we can leverage it to make our functions more portable and faster to start. I'll finish with a demo of how we can build functions in different languages, compile them to portable WebAssembly binaries and then use OpenFaaS to manage and deploy them the same way we do with traditional functions.