A cartoon intro to WebAssembly

WebAssembly is a way of taking code written in programming languages other than JavaScript and running that code in the browser. So when people say that WebAssembly is fast, what they are comparing it to is JavaScript. Now, I don’t want to imply that it’s an either/or situation — that you’re either using WebAssembly or using JavaScript. In fact, we expect that developers will use both WebAssembly and JavaScript in the same application.

Source: hacks.mozilla.org