4 Open Source alternatives to Slack in 2026
We compare 4 self-hostable tools you can deploy on your own server in minutes, with license, tech stack and a ready-to-copy docker-compose.
Quick comparison
Sorted by featured first, then GitHub stars as a tiebreaker — the same rule we use across the whole site.
| Tool | License | Minimum RAM | Docker | GitHub |
|---|---|---|---|---|
| Rocket.Chat Most popular on GitHub1-Click Deploy | MIT | ~1GB | ✅ | ★ ~41,000 |
| Mattermost 1-Click Deploy | MIT | ~1GB | ✅ | ★ ~30,000 |
| Zulip Lightest option100% FOSS | Apache-2.0 | ~512MB | ✅ | ★ ~21,000 |
| Huly 100% FOSS | AGPL-3.0 | ~1GB | ✅ | ★ ~11,000 |
Detailed profile of each alternative
Alternative to Slack
Self-hostable team chat, an alternative to Slack.
Alternative to Slack, Microsoft Teams
Security-focused team chat and collaboration, an alt. to Slack.
Alternative to Linear, Notion, Slack
Projects + chat + docs in one, an alternative to Linear/Notion/Slack.
Alternative to Slack
Team chat organized by threads, an alternative to Slack.
How do I replace Slack?
A practical guide with the real use case and limitation of each of the 4 alternatives, to pick the one that fits best.
See replacement guide →How much does Slack cost, and how much can you save?
Slack costs $8.75/mo per user. Self-hosting the alternative, you only pay for the server — usually a few dollars a month.
Calculate your exact savings in the SaaS Audit →Already know which one you want?
Add Rocket.Chat to the Stack Builder and generate a ready-to-deploy docker-compose.yml, alone or alongside the rest of your stack.
Build my stackFrequently asked questions
Do I need Docker to self-host a Slack alternative?
Yes, for all 4: each one has a ready-to-copy docker-compose.yml. You just need Docker installed on your server.
How much RAM do I need at minimum?
The lightest option on this list is Zulip, which runs on as little as 512MB of RAM — enough for a cheap VPS.
Are they all 100% free, or are there paid features like on Slack?
2 out of 4 are 100% FOSS. The rest are Open-Core: the core is free and self-hostable, but some advanced feature may stay paid — we call it out on each tool's page.