Zulip at a glance
Checked 15 Oct 2026Zulip is a mature, fully open source (Apache-2.0) team chat where every message sits in a named topic inside a channel, which suits async work. Self-hosting needs Ubuntu 22.04+ or Debian 12+, 2 GB RAM plus swap (4 GB and 2 CPUs for 100+ users) and 10 GB disk. Mobile push notifications go through Zulip's service, which needs a paid or sponsored plan above 10 users. Calls are not built in: Zulip adds a link to Jitsi, Zoom or another provider.
RepoQuarry. “Zulip.” Checked 15 Oct 2026. https://repoquarry.dev/projects/zulipHow much of Slack does it replace?
4 of 5 jobs. Topic threading replaces Slack threads; no built-in huddles (call links via Jitsi or Zoom). Mobile push above 10 users needs a plan.
For voice and video huddles, see other Slack alternatives. You may also need to build an interface, an API server and hosting yourself.
Facts, with sources
Every answer links to where we found it. We read the documentation; we did not install it.
Ubuntu 22.04, Ubuntu 24.04, Ubuntu 26.04, Debian 12, and Debian 13zulip.readthedocs.io · requirements.html ↗ 1d ago
Apache License Version 2.0github.com · LICENSE ↗ 1d ago
Organizations with more than 10 users must upgrade their plan in order to access the Mobile Push Notification Service.zulip.readthedocs.io · mobile-push-notifications.html ↗ 1d ago
For installations with 100+ users you’ll need a minimum of 2 CPUs and 4 GB RAM .zulip.readthedocs.io · requirements.html ↗ 1d ago
Ubuntu 22.04, Ubuntu 24.04, Ubuntu 26.04, Debian 12, and Debian 13zulip.readthedocs.io · requirements.html ↗ 1d ago
The installer takes a few minutes to run, as it installs Zulip’s dependencies.zulip.readthedocs.io · install.html ↗ 1d ago