Firefox Runs Inside Chrome as a WebAssembly Build

A project compiles Firefox into WebAssembly and runs it inside Chrome, per Simon Willison's July 17 post. The novelty is fun. The real story is sandboxing. A full browser engine sealed inside a Wasm boundary could let an agent browse the web without ever touching the host machine. That's a complete rendering and JavaScript engine walled off from whatever system it runs inside.

Willison put it simply: "Here's my blog, running in Firefox, running in WebAssembly, running in Chrome."

Agent-driven browsing carries real risk when the agent runs with host-level access instead of a sealed boundary. Claude Code's sandbox and credential disclosures are the concrete reason that risk is getting attention.

Willison's post doesn't say the project was built with agent isolation in mind. It also doesn't address performance, or whether the trick holds outside a demo.

Whether any agent framework actually ships a Wasm-sandboxed browser, rather than just talking about isolation, is the thing worth watching.