WebAssembly is the browser’s virtual machine. It is a binary code that runs in the browser and is already available today in most of the browsers. This will change the way how client applications will be developed in the future. The technologies for client development will shift at least partially from JavaScript and similar technologies towards compiled code like Java, Rust, Golang, Swift – real programming languages. The talk will introduce the architecture of WebAssembly, where it is today, and what can be expected in the future. It also explains why it is important for Java developers to pay attention to this technology in their future carreer.