If you’re looking to move off Slack, you have options. Real ones. Here are the 4 open-source, self-hostable alternatives I’ve tested, with honest notes on what each does well and where each falls short.
Why leave Slack?
- Free tier now hides messages older than 90 days.
- Paid tier scales per user — $8.75/user/mo adds up quickly.
- AI features quietly train on your team’s messages by default.
The 4 best self-hosted alternatives to Slack
Mattermost
The most polished self-hosted Slack. Mobile + desktop apps, threads, integrations, decent free tier.
Visit Mattermost website →Rocket.Chat
More features than Mattermost (voice, video, omnichannel). Heavier to run.
Visit Rocket.Chat website →Zulip
Threaded model instead of channels — cleaner for async work. Excellent search.
Visit Zulip website →Element / Matrix
Federated protocol. Best for privacy-focused, cross-org communication. Setup is more involved.
Visit Element / Matrix website →Quick comparison
| Alternative | Difficulty | License |
|---|---|---|
| Mattermost | Medium | AGPL-3.0 / Apache-2.0 |
| Rocket.Chat | Medium | MIT |
| Zulip | Medium | Apache-2.0 |
| Element / Matrix | Hard | AGPL-3.0 |
Frequently asked questions
Is there a free alternative to Slack?
Yes. Every tool listed above is free and open source. Some, like Mattermost, also have optional paid hosted tiers if you don’t want to run the server yourself. Everything else is genuinely free to self-host — you pay only for your own hardware and time.
Which one should I pick if I’ve never self-hosted anything before?
Start with Mattermost. It’s the lowest-friction option here — realistic to have running in an afternoon on a small server or Raspberry Pi. If it doesn’t fit your workflow, Rocket.Chat is a good second try.
Can I run these on a Raspberry Pi?
Most of them, yes — the tools marked Easy here will comfortably run on a Pi 4 or Pi 5 with 4GB+ of RAM. The Medium tools may work but appreciate a mini PC or a spare desktop. Hard-tagged tools generally want real server hardware.
What about mobile apps?
It varies. Tools like Vaultwarden and Immich have native iOS/Android apps that connect to your server. Others rely on the web UI through your phone browser — fine for occasional use, not a full app experience.