Open Source Chat
Team chat becomes the company's memory - every decision, handoff, and half-finished thread lives there, which means the vendor holding that history holds real leverage the day you want to leave or just read what you wrote two years ago. The open source servers here keep that conversation log in a database you run, with the full message archive, files, and integrations exportable on your terms, so the place your team thinks out loud answers to you rather than to a per-seat invoice.
Discourse
Open-source community discussion platform with self-hosting, built-in chat, and themes
Rocket.Chat
Open source team communications platform with messaging, voice, video, federation, and apps
LibreChat
Self-hosted AI chat platform with model switching, agents, MCP, and multi-user access
Mattermost
Open source self-hosted collaboration platform with chat, workflow automation, voice, and screen sharing
Chatwoot
Open-source customer support platform for live chat, email, and omnichannel inboxes
Jitsi Meet
Open source video conferencing for browsers, mobile apps, self-hosted servers, and embedded meetings
Huly
Open-source team platform combining project management, chat, CRM, HRM, and applicant tracking
Zulip
Open source team chat with topic-based threading for live and asynchronous conversations
SimpleX Chat
Private messenger with no user IDs, link or QR based connections, and double ratchet end to end encryption