Zulip
Topic-threaded team chat purpose-built for async, high-signal discussion.
Self-hosted Open source Apache 2.0 chatasyncopen-source
Pricing
Free (self-hosted). Cloud from $8.30/user/month, free for open-source projects.
Zulip organizes every message into a topic within a channel, which sounds minor until you’ve used it — conversations don’t collapse into an unreadable single stream the way most chat tools do.
Key features
- True topic threading, not just replies
- Excellent for distributed, async-first teams
- Fully open source, including the Cloud codebase
- Generous free tier for open-source projects
Self-hosted vs. cloud
Self-host with Docker or a native install; Zulip Cloud is the managed option with the same feature set, priced per user.
Quick start
git clone https://github.com/zulip/zulip-docker.git
cd zulip-docker && docker compose up -d
Alternatives
Mattermost’s model is closer to Slack if your team is more sync/real-time than async.