Zulip is an open-source team chat application with a threading model built around topics within channels, rather than flat message streams. This makes it unusually suited to async-heavy teams: conversations are easy to follow days later without reading everything in between. It can be self-hosted on any Linux server or used via Zulip Cloud, including a free tier for open-source projects.
Reviewed by Marco Wollank
Zulip
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Threat level
Covered
A covered pick. Anyone can use it as a private drop-in, with no setup or know-how. Enough for most people. Threat levels
Our take
Zulip’s topic threading is a genuine architectural difference from Slack, not just a feature flag, and teams that work across time zones often find it significantly less exhausting to stay current. The trade-off is a higher learning curve: the channel-plus-topic model confuses people used to Slack’s flat channels, and onboarding needs more upfront explanation. The self-hosted path gives you full data ownership with no ongoing vendor dependency. If your team already communicates well in Slack, switching takes real effort; if you are starting fresh or currently drowning in missed messages, Zulip is worth the adjustment.
GitHub at a glance
zulip/zulip
Stars
25,511
+ 123 this week
Last commit
15d ago
healthy
License
Apache-2.0
Latest release
12.1
21d ago
Stars, last 38d
Website at a glance
zulip.com
B score 70
Solid website security headers
Graded by Mozilla HTTP Observatory, tested 4d ago
Inspect this site yourself
Measures the security configuration of the tool's own website, not the privacy of the product itself. A strong tool can still score low here.
Zulip alternatives
Zulip license, in plain English
Apache-2.0 Permissive
Permissive like MIT, with an explicit patent grant and a requirement to flag any changes you make.
Permits
- Commercial use
- Modification
- Distribution
- Patent use
- Private use
Requires
- License and copyright notice
- State changes
Does not provide
- Trademark use
- Liability cover
- Warranty
Why it matters: Permissive licensing lets anyone reuse this, including inside closed products. That is freedom to build on, but no guarantee that downstream copies stay open.
Plain-language summary of the project's license, not legal advice. Read the full text for the exact terms.
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