Concord is peer-to-peer, end-to-end encrypted group chat: guilds, channels, direct messages, voice, video and screen sharing. There is no account server and no message store. Each guild is an MLS group (RFC 9420), and history lives on the members' devices.

curl -fsSL https://zahakj.github.io/concord/install.sh | sh

That installs the single-file build for Linux or macOS into ~/.local/bin after checking it against the release's SHA256SUMS. Run concord and your browser opens on the app. Windows, the native desktop apps and Android are on the releases page.

Using it

Pick a passphrase; the first unlock creates your identity, an Ed25519 keypair stored on the device. Create a guild and send its invite code to a friend.

Two peers must be able to reach each other:

Where you are	What it takes
Same Wi-Fi, or the same Tailscale/WireGuard mesh	Nothing.
One side can forward a port	One router rule. The invite code carries that address.
Neither can	Someone in the group runs a rendezvous: one small always-on node that introduces peers and relays ciphertext.

Can people reach me? in the command palette (Ctrl+K) reports which row you are in.

Features

• Guilds with channels, categories, forums, roles and permissions
• Replies, edits, reactions, pins, mentions, polls, events, Markdown
• Direct messages, delivered through an encrypted offline mailbox when the recipient is away; message requests from strangers
• Voice, video and screen sharing over a WebRTC mesh; push-to-talk
• Meeting rooms that guests can join from a browser without installing
• Encrypted attachments, custom emoji, local full-text search, Markdown export
• Several devices per identity, linked by QR code
• Import of an exported community's history into a guild archive
• Bots: a script with its own identity, speaking JSON lines
• Desktop apps for Linux and Windows, a browser-served build for Linux, macOS and Windows, and Android

Emoji, fonts, icons and sounds are compiled in. Nothing is fetched from a third party unless you switch on a feature that says it will; PRIVACY.md lists every outbound request the app can make.

Building

Go (version in go.mod) and Node 22+.

git clone https://github.com/ZahakJ/concord && cd concord
make web          # -> bin/concord-web, serves the UI on 127.0.0.1:8787
make gui          # native window, needs webkit2gtk-4.1
make peers        # two isolated local peers for development
make help         # everything else

Documentation

The manual is at zahakj.github.io/concord/manual: installing on each platform, guilds, calls, devices, backups, privacy, moderation and troubleshooting, with developer pages on the architecture, protocol, building and testing. Its sources are the Markdown in docs/manual and docs/dev; the documents below are pages of it too.

DESIGN.md	How it works: identity, discovery, NAT traversal, MLS, sync, threat model
RENDEZVOUS.md	Running the optional node
BOTS.md	Writing a bot
PUSH.md	Optional push wakes
FAQ.md	Common questions
PRIVACY.md	What data exists and who can read it
SECURITY.md	Reporting a vulnerability; known gaps
CONTRIBUTING.md	Development loop, tests, code style
RELEASING.md	Maintainer runbook
WINDOWS.md	SmartScreen and Defender
THIRD-PARTY-NOTICES.md	Bundled assets and licences

The optional meme-template pack is not in the repository; see frontend/public/memes/README.md.

Licence

GNU Affero General Public License, version 3 or later. See LICENSE.