permissionlesstech/bitchat: Trending on GitHub
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
📲 App Store
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 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 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 on identity and metadata for what a nearby radio can observe
Private Message End-to-End Encryption: Noise Protocol 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
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 optimized for Bluetooth LE constraints
Automatic Discovery: Peer discovery and connection management
Adaptive Power: Battery-optimized duty cycling
Nostr Protocol (Internet)
Global Reach: Connect with users worldwide via internet relays
Location Channels: Geographic chat rooms using geohash coordinates
290+ Relay Network: Distributed across the globe for reliability
BitChat Private Envelopes: App-specific encrypted private messages over Nostr relays
Ephemeral Keys: Fresh cryptographic identity per geohash area
BitChat's private-envelope format is proprietary and is not NIP-17, NIP-44, or NIP-59 compatible. It uses Nostr as a relay transport but only interoperates with BitChat clients: private payloads travel inside kind-1059 events whose v2:-prefixed content is a BitChat-specific XChaCha20-Poly1305 construction, not NIP-44 encryption.
Channel Types
mesh #bluetooth
Transport: Bluetooth Low Energy mesh network
Scope: Local devices within multi-hop range
Internet: Not required
Use Case: Offline communication, protests, disasters, remote areas
Location Channels (block #dr5rsj7, neighborhood #dr5rs, country #dr)
Transport: Nostr protocol over internet
Scope: Geographic areas defined by geohash precision
block (7 chars): City block level
neighborhood (6 chars): District/neighborhood
city (5 chars): City level
province (4 chars): State/province
region (2 chars): Country/large region
Internet: Required (connects to Nostr relays)
Use Case: Location-based community chat, local events, regional discussions
Direct Message Routing
Private messages use intelligent transport selection:
Bluetooth First (preferred when available)
Direct connection with established Noise session
Fastest and most private option
Nostr Fallback (when Bluetooth unavailable)
Uses recipient's Nostr public key
BitChat's app-specific private-envelope encryption
Routes through global relay network
Smart Queuing (when neither available)
Messages queued until transport becomes available
Automatic delivery when connection established
For detailed protocol documentation, see the Technical Whitepaper.
Setup
Option 1: Using Xcode
open bitchat.xcodeproj
For a signed device build, create your ignored local configuration and replace the example team ID with your Apple Developer Team ID:
cp Configs/Local.xcconfig.example Configs/Local.xcconfig
Local.xcconfig.example derives unique app and App Group identifiers from that team ID. The entitlement files already reference $(APP_GROUP_ID), so tracked project or entitlement files do not need to be edited.
Useful command-line checks from the repository root:
macOS Debug build without signing
xcodebuild -project bitchat.xcodeproj -scheme "bitchat (macOS)"
-configuration Debug CODE_SIGNING_ALLOWED=NO build
Full SwiftPM test suite
swift test
iOS simulator tests
xcodebuild -project bitchat.xcodeproj -scheme "bitchat (iOS)"
-sdk iphonesimulator
-destination 'platform=iOS Simulator,name=iPhone 17' test
If iPhone 17 is unavailable, choose an installed simulator from:
xcodebuild -showdestinations -project bitchat.xcodeproj -scheme "bitchat (iOS)"
Option 2: Using just
brew install just just check just run
just build and just run use the current bitchat (macOS) scheme and keep Xcode output in the ignored .DerivedData/ directory. They never patch source, project, configuration, or entitlement files.
just clean removes only .DerivedData/ and .build/. It does not invoke Git or restore tracked files, so uncommitted work is preserved. just test runs the SwiftPM suite and just test-ios runs the iPhone 17 simulator suite.
Localization
App localizations live in bitchat/Localizable.xcstrings.
Share extension strings are separate in bitchatShareExtension/Localization/Localizable.xcstrings.
Prefer keys that describe intent (app_info.features.offline.title) and reuse existing ones where possible.
Run xcodebuild -project bitchat.xcodeproj -scheme "bitchat (macOS)" -configuration Debug CODE_SIGNING_ALLOWED=NO build to compile-check any localization updates.
