Open Source Alternatives
Alternatives to Slack
Team messaging and collaboration platform.
Slack is a trademark of its respective owner.
Updated May 2026
What you gain
- ✓No per-user pricing that grows with every employee
- ✓Full message history without paying for search access
- ✓No message archive limits on the free tier
- ✓Self-hosted deployment for compliance and data sovereignty
What you give up
- △No Slack Connect for cross-organization channels
- △No Huddles for instant audio/video calls from any channel
- △No 2,600+ prebuilt app integrations in the Slack Marketplace
- △No Workflow Builder for no-code channel automation
Switching Cost
Slack's lock-in is the integration graph and team habits. Messages export via the Slack Export tool (admins only), but the 2,600+ app integrations, custom Workflow Builder automations, and Slack Connect cross-org channels don't transfer. Teams under 20 people can switch in a day if everyone commits. Enterprise orgs with hundreds of channels, custom apps, and Slack Connect partners should budget 2-4 weeks for the technical migration and months for full adoption. The hidden cost is the productivity dip: your team has years of muscle memory in Slack, and that takes time to rebuild.
| Mattermost | Rocket.Chat | Zulip | |
|---|---|---|---|
| Overlap | 85% | 82% | 78% |
| Migration | moderate | moderate | moderate |
| License | MIT + AGPL | MIT License | Apache License 2.0 |
| Best for | Small teams | Teams with DevOps | Teams with DevOps |
We find the alternatives so you don't have to
Open source analysis in your inbox every Wednesday.
Drop-in Replacements
Ranked by feature coverage
Mattermost
7385% coverageOpen source secure collaboration platform
Channels, threads, file sharing, integrations, video calls. It looks and works like Slack because that's exactly what it's replacing.
Rocket.Chat
8182% coverageOpen source Slack/Teams alternative
Rocket.Chat is a self-hosted messaging platform where you control the data and no vendor decides to change pricing on you. battle-tested, used by government agencies and enterprises that can't put conversations on someone else's cloud.
Zulip
8378% coverageTeam chat with threading
Zulip fixes chat overload with threading that actually works. Every message belongs to a topic within a stream (channel).
Building Blocks
Slack is a platform. It bundles multiple capabilities into one subscription. These tools each cover one piece. Teams often assemble 2–3 of them instead of paying for the full suite.
AWS Cognito