Open-source alternatives to Slack
4 alternatives, ranked by a published maintenance score computed from live GitHub signals (fetched 2026-09-04). We flag unmaintained projects on both sides — including Slack itself when the data says so.
About Slack: Proprietary SaaS; free tier now hides history past 90 days, a common trigger for alternative-hunting. It is closed-source, so the same public maintenance signals do not exist for it — we score only the alternatives below.
The alternatives
Mattermost
Self-hostable team chat with channels, threads, and integrations.
How this 90/100 was computed
| Last commit | today | 40/40 |
|---|---|---|
| Latest release | 9 days ago | 25/25 |
| Community size | GitHub stars | 15/15 |
| Open-issue trend | not enough history yet — needs snapshots 21+ days apart; neutral 10/20 awarded meanwhile | 10/20 |
| Total | 90/100 |
Rocket.Chat
Self-hostable chat platform with federation and omnichannel features.
How this 90/100 was computed
| Last commit | today | 40/40 |
|---|---|---|
| Latest release | yesterday | 25/25 |
| Community size | GitHub stars | 15/15 |
| Open-issue trend | not enough history yet — needs snapshots 21+ days apart; neutral 10/20 awarded meanwhile | 10/20 |
| Total | 90/100 |
Zulip
Threaded team chat; every message belongs to a topic.
How this 90/100 was computed
| Last commit | today | 40/40 |
|---|---|---|
| Latest release | 25 days ago | 25/25 |
| Community size | GitHub stars | 15/15 |
| Open-issue trend | not enough history yet — needs snapshots 21+ days apart; neutral 10/20 awarded meanwhile | 10/20 |
| Total | 90/100 |
Element
Matrix-protocol client; decentralized, end-to-end encrypted rooms.
How this 87/100 was computed
| Last commit | today | 40/40 |
|---|---|---|
| Latest release | 3 days ago | 25/25 |
| Community size | GitHub stars | 12/15 |
| Open-issue trend | not enough history yet — needs snapshots 21+ days apart; neutral 10/20 awarded meanwhile | 10/20 |
| Total | 87/100 |