permissionlesstech/bitchat

Bitchat is a decentralized messaging app for iPhone and Mac that lets people chat without any central servers, phone numbers, or accounts. It has two modes that work together: a local Bluetooth mesh network for offline communication, and a global internet protocol called Nostr for reaching people anywhere in the world. The Bluetooth mesh part is genuinely unusual, it lets your phone relay messages through a chain of nearby devices even when there is no internet. If you and a group of people are at a protest, disaster zone, or remote area, messages can hop from phone to phone (up to 7 hops) to reach someone outside your immediate Bluetooth range. No internet required. When internet is available, the app switches to Nostr, a decentralized messaging network with no central company controlling it, and can connect to geographic chat rooms based on your location (neighborhood, city, region). Private messages are end-to-end encrypted using strong cryptographic protocols. The design is deliberately privacy-first: no sign-up, no phone number linked to your identity, and there is even an emergency triple-tap to instantly wipe all data from the phone. Built natively in Swift for iOS and macOS, the app is available on the App Store now. The code is open-source and released into the public domain, meaning anyone can modify or redistribute it freely. For a founder: this is a finished, deployable app rather than a library or tool. It is interesting as a reference for building offline-capable, privacy-preserving communication features.