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Zulip

★ 23k

Team chat with threaded topics that actually scale to busy channels. Loved by open-source orgs that left Slack.

Zulip does the job of Slack, self-hosted. It is Apache-2.0-licensed, so you can do essentially what you like with it, and setting it up is an afternoon, not a weekend. Slack bills $8/user/mo for it. 23k stars on GitHub.

Open-source replacement for Slack.

Licence
Apache-2.0
Self-hosting
Medium
The paid one costs
$8/user/mo
GitHub stars
23k
view the code →official site →

Is it actually a replacement?

We have written a verdict on what it replaces — what you lose, and why people still pay:

How Zulip runs

Where it runs

Zulip runs on your machine or their cloud.

Installing it

Hosted signup, or run the official install script/Docker deployment on supported Ubuntu or Debian.

Where your data lives

Persistent messages and organization data in PostgreSQL; uploads locally or in S3-compatible storage; exports are tar.gz archives containing JSON and files.

What setup takes

Free cloud search stops at 10,000 messages; self-hosting needs a Linux VM, DNS/TLS, outgoing email and at least about 2 GB RAM.

The catch compared with Twist

Zulip is the closest structural match, but its free cloud search stops at 10,000 messages and self-hosting replaces Twist's managed operations with a Linux service.

Zulip questions

Is Zulip open source?

Yes — it is released under Apache-2.0.

Can Zulip replace Slack?

Our verdict on Slack Pro is YES. Rocket.Chat Community (46k stars), Discourse (44k stars), Mattermost Team Edition (39k stars) are mature open-source replacements for Slack Pro — self-host with real ops work and stop paying $8.75/mo.

Can I self-host Zulip?

Yes — we rate it medium to self-host, and it runs on your machine or their cloud. Hosted signup, or run the official install script/Docker deployment on supported Ubuntu or Debian.

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