Open-Source Alternatives to Slack
Based on our dataset, the self-hostable open-source alternatives to Slack are Mattermost and Zulip. The Slack plan we benchmark is Pro ($8.75/seat/mo).
Data last updated . How we check.
Quick comparison
| Alternative | License | RAM in starter config | Needs Postgres / Redis | Migration |
|---|---|---|---|---|
| Mattermost | MIT / AGPL-3.0 | 1024 MB | Yes / No | Easy (Slack export ZIP importer) |
| Zulip | Apache-2.0 | 1536 MB | Yes / Yes | Easy |
Mattermost
Enterprise-grade open-source team messaging, playbooks, and voice calls
- Slack-compatible webhooks & slash commands
- Built-in voice calls & screen sharing
- Unlimited searchable history forever
Docker image mattermost/mattermost-team-edition:release-10. GitHub: mattermost/mattermost (31.5k stars when our data was last updated). Website: https://mattermost.com
Zulip
Organized threaded team chat designed for deep async work and distributed engineering teams
- Topic-based threading prevents chat chaos
- 100+ native integrations
- Fast mobile & desktop apps
Docker image zulip/docker-zulip:latest. GitHub: zulip/zulip (22.1k stars when our data was last updated). Website: https://zulip.com
Switching from Slack
- Pick an alternative above and open its comparison page for the cost breakdown.
- Generate a free starter
docker-compose.ymlin the stack builder. - Test it on a small server with a copy of your data before moving the team over.
- Check the migration notes in the table, and the official docs of the tool you pick.
More detail: Replace Slack guide.
FAQ
What are the open-source alternatives to Slack?
In the StackSwitcher dataset, the self-hostable open-source alternatives to Slack are Mattermost, Zulip.
Which Slack plan does StackSwitcher compare against?
We benchmark Slack Pro ($8.75/seat/mo). The main pain point we note: 90-day message history paywall on free plan; $1,050+/yr for a 10-person team just to search old messages.
How much RAM does Mattermost need when self-hosted?
Our starter Docker config budgets 1024 MB of RAM for Mattermost plus Postgres. Real needs depend on your usage.
How much RAM does Zulip need when self-hosted?
Our starter Docker config budgets 1536 MB of RAM for Zulip plus Postgres and Redis. Real needs depend on your usage.
Config templates are MIT licensed and provided "AS IS", with no warranty of any kind and no liability. Prices and specs are informational estimates from our dataset, so check the vendor and project sites before you decide. See the Terms & No Warranty disclaimer.