A founding engineer shares hard-won lessons from building Sail and Muddy, two multiplayer browsers developed by a small team that raised $5.5 million in seed funding from General Catalyst, Naval, Lachy Groom, and Y Combinator in 2022. They built directly on a Chromium fork, leveraging web technologies for the UI while accessing browser internals like tabs and history APIs. Their initial vision: "a window worthy of the work you do with other people" — an infinite canvas combining websites, text, cursors, and real-time collaboration.

Sail never got a broad public launch. The team tested it with different user types but failed to reach the specific audience that might have loved it — a positioning problem they should have tackled head-on. Paul Graham's warning about working in secret proved accurate: "The danger of working in secret is inversely proportional to the simplicity and precision of the test." Brian Chesky's advice hits harder in hindsight — Airbnb launched three times before finding traction. Taking too long to launch builds pressure and protects a reputation you haven't earned yet.

After Sail, they pivoted to the "multiverse project" — supporting infinite canvas, structured canvas, and chat simultaneously. It got complex fast. Chat survived as Muddy: "Slack and a browser as an integrated work environment." Chat is lindy — people understand it immediately and it transfers to mobile. But they overindexed on table stakes like the mobile app while positioning remained too close to Slack. Building a browser product was unusually hard, and even though it didn't work out as a company, the team proved a lot and learned a lot.