The maturation of the Web platform has given rise to sophisticated and demanding Web applications such as interactive 3D, audio and video software, and games. Efficiency and security of mobile code on the Web has become more important than ever. Yet JavaScript as the universal language of the Web is poorly equipped to meet these requirements, especially as a compilation target.

Engineers from all major browser vendors have risen to the challenge and collaboratively designed a portable low-level byte code called WebAssembly. It offers compact representation, efficient validation and compilation, and safe low-overhead execution. Rather than committing to a specific programming model, WebAssembly is an abstraction over modern hardware, making it language-, hardware-, and platform-independent, with use cases beyond just the Web. WebAssembly is the first industrial-strength language that has been designed with a formal semantics from the start.

This talk will present the motivation, design and formal semantics of WebAssembly and preliminary experience with implementations.