The alternatives
Rocket.Chat
The Secure CommsOS™ for mission-critical operations
RocketChat/Rocket.Chat Updated 2026-05-01 Rocket.Chat
The Secure CommsOS™ for mission-critical operations
rocketchat/Rocket.Chat Updated 2026-04-23 mattermost
Mattermost is an open source platform for secure collaboration across the entire software development lifecycle..
mattermost/mattermost Updated 2026-05-01 zulip
Zulip server and web application. Open-source team chat that helps teams stay productive and focused.
zulip/zulip Updated 2026-04-30 element-web
A glossy Matrix collaboration client for the web.
element-hq/element-web Updated 2026-04-30 discussions
Repository for miscellaneous repository management and discussions: https://github.com/revoltchat/revolt/discussions
revoltchat/revolt Updated 2026-02-16 Comparison notes
OSS alternatives typically require self-hosting and operational effort in exchange for predictable cost and full data control. Feature parity varies — evaluate each option against your specific workflow before committing.
Migration tips
- Export data from the SaaS before migration (most provide CSV/JSON exports)
- Pilot the OSS alternative with a subset of your team before full rollout
- Budget for self-hosting infrastructure and maintenance time
FAQ
Can I fully replace Slack with an OSS tool?
Feature parity varies. Most OSS alternatives cover 70-90% of core workflows, but may lack polish, integrations, or specialized features. Pilot the alternative with a subset of your team before fully committing.
What's the cost of self-hosting?
Plan for ~$5-50/month in VPS costs (DigitalOcean, Hetzner, etc.) plus 2-8 hours/month in maintenance. For a team of 20+, self-hosting usually breaks even against SaaS pricing within 6-12 months.
Which alternative should I pick?
Sort by GitHub stars (a proxy for community health), check the last-pushed date (avoid unmaintained projects), and read recent issues to gauge responsiveness.