You've likely had WebAssembly running in your browser but didn't even realize it.

Firefox also lets add-ons run WebAssembly modules which is something that uBlock Origin has made use of for a long time:

https://github.com/gorhill/uBlock/wiki/uBlock-Origin-works-b...

1Password actually bundles it with everything they ship (browser, desktop, even their golang cli): https://github.com/1Password/onepassword-sdk-go/tree/v0.1.7/... and then use extism to cross over its boundary https://github.com/1Password/onepassword-sdk-go/blob/v0.1.7/...

They compiled their rust libraries to wasm and it allows reuse of those rust bits across everything

The other famous example I know of, but haven't used, is Figma https://www.figma.com/blog/webassembly-cut-figmas-load-time-...