2026-07-16 23:34 UTCOriginal source1 min readUpdated: 2026-07-17 00:13 UTC

Firefox in WebAssembly

Puter compiled Firefox to WebAssembly, enabling a full browser to run inside another browser. The project used an estimated $25,000 in Claude Opus and Fable tokens, leverages the Wisp protocol for proxying, supports end-to-end encryption, and is open source.

SourceSimon Willison's Weblog

Simon Willison’s Weblog

16th July 2026 - Link Blog

Firefox in WebAssembly (via) This is absurdly cool: Puter compiled Firefox to WebAssembly such that the whole browser runs in another browser.

Here's my blog, running in Firefox, running in WebAssembly, running in Chrome:

They chose Firefox/Gecko because it has strong single-process support. The project took an estimated $25,000 of Claude Opus and Fable tokens, taking advantage of a Claude Max subscription plan.

The demo funnels all traffic over a WebSocket protocol (using the Wisp protocol) through Puter's server - a requirement to get this kind of thing to work because code running in browsers can't open arbitrary network connections.

(That proxying sounds expensive! The team had to scale the servers up to handle the traffic during the Hacker News conversation about the project.)

Puter claim this supports end-to-end encryption and that looks to be true - I inspected the WebSocket messages and traffic to my own HTTPS site was encrypted whereas requests and responses to http://www.example.com/ were in cleartext.

Here's the repo for firefox-wasm. theogbob/WebkitWasm is a similar project that compiles WebKit to WASM, but that one doesn't currently have an accessible online demo.