Web pages have long relied on a single scripting language, which is flexible but not ideal for heavy computation. WebAssembly is a compact, low-level format that browsers can run at close to native speed, letting code written in many languages run safely inside a page.
It is sandboxed, so it cannot reach outside the browser's controlled environment, and it works alongside existing scripts rather than replacing them. This makes tasks like image editing, simulations and games practical in a browser without installing anything.