Community-driven Instant Messaging Network
Mattermost is an open source, self-hosted Slack-alternative
An IRC like chat system
Create, share, communicate, chat and call securely, and bridge to other apps! Compatible with Matrix.
Rocket.Chat is free, unlimited and open source. Replace email, HipChat & Slack with the ultimate team chat software solution.
Roll Call is a completely free🎉 voice chat service with podcast quality recording.
Zulip combines the immediacy of real-time chat with an email threading model. With Zulip, you can catch up on important conversations while ignoring irrelevant ones.