Stoat

Open-source chat platform (formerly Revolt) founded in 2021, developed by a team of friends who wanted to create a user-first chat app. Fully open-source under AGPL-3.0 with clients for web, desktop, Android, and iOS. Backend written in Rust, frontend in TypeScript/Solid.js. 600k+ users, 150k+ lines of code. Headquartered in London, UK.