bitchat

<img width="256" height="256" alt="icon_128x128@2x" src="https://github.com/user-attachments/assets/90133f83-b4f6-41c6-aab9-25d0859d2a47" />

## bitchat

A decentralized peer-to-peer messaging app with dual transport architecture: local Bluetooth mesh networks for offline communication and internet-based Nostr protocol for global reach. No accounts, no phone numbers, no central servers. It's the side-groupchat.

[bitchat.free](http://bitchat.free)

📲 [App Store](https://apps.apple.com/us/app/bitchat-mesh/id6748219622)

📲 [Play Store](https://play.google.com/store/apps/details?id=com.bitchat.droid)

### Getting a copy you can trust

Install from the App Store, or build from source you have verified. A compiled build from anywhere else cannot be verified — see [Verifying bitchat](docs/VERIFYING-A-BUILD.md) for how to check source against the per-release hash manifest, and for what to do if that is the only build you can get.

This matters more than it usually would: this repository has been the target of takedown demands, and when a repository or releases page disappears, mirrors appear that nobody can check.

## License

This project is released into the public domain. See the [LICENSE](LICENSE) file for details.

## Features

- **Dual Transport Architecture**: Bluetooth mesh for offline + Nostr protocol for internet-based messaging
- **Location-Based Channels**: Geographic chat rooms using geohash coordinates over global Nostr relays
- **Intelligent Message Routing**: Automatically chooses best transport (Bluetooth → Nostr fallback)
- **Decentralized Mesh Network**: Automatic peer discovery and multi-hop message relay over Bluetooth LE
- **Privacy First**: No accounts, no phone numbers, no servers. Note that the mesh does use a persistent per-device identifier derived from your identity key — see [the whitepaper](WHITEPAPER.md) on identity and metadata for what a nearby radio can observe
- **Private Message End-to-End Encryption**: [Noise Protocol](https://noiseprotocol.org) for mesh, BitChat private envelopes for Nostr fallback
- **IRC-Style Commands**: Familiar `/slap`, `/msg`, `/who` style interface
- **Universal App**: Native support for iOS and macOS
- **Emergency Wipe**: Triple-tap to instantly clear all data
- **Performance Optimizations**: LZ4 message compression, adaptive battery modes, and optimized networking

## [Technical Architecture](https://deepwiki.com/permissionlesstech/bitchat)

BitChat uses a **hybrid messaging architecture** with two complementary transport layers:

### Bluetooth Mesh Network (Offline)

- **Local Communication**: Direct peer-to-peer within Bluetooth range
- **Multi-hop Relay**: Messages route through nearby devices (max 7 hops)
- **No Internet Required**: Works completely offline in disaster scenarios
- **Noise Protocol Encryption**: End-to-end encryption, with forward secrecy for live sessions (store-and-forward mail is sealed without it — see the whitepaper)
- **Binary Protocol**: Compact packet format opti