Open source alternatives · Productivity
Open Source Alternative to Slack
Slack costs US$8.75 per user monthly and deletes old messages on free plans. Mattermost is the open-source team chat you own.
What the paid app costs: US$8.75/user/mo
Why switch?
Team chat holds your company's memory. On Slack's free tier that memory gets deleted after 90 days unless you pay per head. Self-hosted Mattermost or Zulip keeps every message forever, on hardware you control, at zero per-user cost.
Compare the alternatives
| Alternative | License | Platforms | Best for |
|---|---|---|---|
| Mattermost | AGPL-3.0 / Apache-2.0 | Windows, macOS, Linux, iOS, Android, web | The open-source Slack for teams |
| Zulip | Apache-2.0 | Windows, macOS, Linux, iOS, Android, web | For communities drowning in chat noise |
| Rocket.Chat | AGPL-3.0 | Windows, macOS, Linux, iOS, Android, web | For all-in-one team communication |
Mattermost
Free forever AGPL-3.0 / Apache-2.0 · Windows, macOS, Linux, iOS, Android, web
- Slack-style channels and threads
- Self-host for full privacy
- Calls and playbooks built in
The open-source Slack for teams
Zulip
Free forever Apache-2.0 · Windows, macOS, Linux, iOS, Android, web
- Topic-based threading
- Built for large communities
- 100,000s of messages searchable
For communities drowning in chat noise
Rocket.Chat
Free forever AGPL-3.0 · Windows, macOS, Linux, iOS, Android, web
- Channels, video, and omnichannel
- Federation support
- Self-hostable
For all-in-one team communication
Which one should you pick?
- Mattermost: The open-source Slack for teams
- Zulip: For communities drowning in chat noise
- Rocket.Chat: For all-in-one team communication
Frequently asked questions
Can I migrate my Slack history?
Yes, Mattermost and Zulip both import Slack export files, including channels and users.
Is self-hosting chat hard?
Both ship Docker images; a small team runs fine on a $5/month VPS or a spare machine.
What about video calls?
Mattermost has built-in calls; Zulip and Rocket.Chat integrate with Jitsi for free video meetings.