Firefox Compiled to WebAssembly and Run Inside Chrome

Puter has released firefox-wasm — a compilation of the Firefox browser to WebAssembly that lets it run right inside another browser. Blogger Simon Willison demonstrated the result: his site opens in Firefox running in WebAssembly inside Chrome.

For the port, the developers chose Firefox and the Gecko engine specifically because of their mature support for single-process operation. By the team's estimate, building the project took roughly $25,000 worth of tokens from the Claude Opus and Fable models, used under a Claude Max subscription.

Since code executed in the browser cannot directly open arbitrary network connections, all of the demo's traffic passes through Puter's servers over the WebSocket protocol using the Wisp protocol. According to the developers, this scheme supports end-to-end encryption — Willison verified it himself by examining the contents of the WebSocket messages: traffic to his HTTPS site turned out to be encrypted, whereas requests to http://www.example.com/ were transmitted in the clear.

Proxying through its own servers meant a noticeable load for the team: after the project was posted to Hacker News, they had to scale up their infrastructure to cope with the increased traffic.

The project's source code is available in the firefox-wasm repository. There is also a similar effort — WebkitWasm, which compiles the WebKit engine to WebAssembly — though it does not yet have a working online demo.

Source: Simon Willison