Alternative to
Open-source alternatives to Slack that still ship
6 open-source startups in this directory are positioned against Slack. 5 pushed code within 30 days of the snapshot of 2026-09-22, 0 have been quiet for 31–120 days, 1 has not pushed in over 120 days. “Alternative to Slack” is a judgment by Jev, TypeSafe’s classifier, made from the repository’s own name, description and homepage, and printed only when it put that match at 0.5 or better. It is not a claim these projects make about themselves, it is not a feature comparison, and Slack has nothing to do with this page.
5 of 6 pushed within 30 days of the snapshot of 2026-09-22. How we measure it →
The list
All 6, most-starred first.
The last column is the most recent push GitHub reported to us on 2026-09-22. It counts a push to any branch, by a person or a bot — it is not a claim that anyone is maintaining the project, and a quiet repository may be a finished one.
| Project | What it does | Stars | Ship status | Last verified push |
|---|---|---|---|---|
| RocketChat/Rocket.Chat | The Secure CommsOS™ for mission-critical operations | 46.2K | Still shipping | Sep 22, 2026 |
| mattermost/mattermost | Mattermost is an open source platform for secure collaboration across the entire software development lifecycle.. | 39.1K | Still shipping | Sep 22, 2026 |
| zulip/zulip | Zulip server and web application. Open-source team chat that helps teams stay productive and focused. | 25.9K | Still shipping | Sep 22, 2026 |
| tinode/chat | Instant messaging platform. Backend in Go. Clients: Swift iOS, Java Android, JS webapp, scriptable command line; chatbots | 13.5K | Still shipping | Sep 13, 2026 |
| element-hq/element-web | A glossy Matrix collaboration client for the web. | 13.5K | Still shipping | Sep 22, 2026 |
| matrix-org/synapse | Synapse: Matrix homeserver written in Python/Twisted. | 12.1K | Gone silent | Apr 26, 2024 |
Related collections
Sideways from here.
The 8 largest other alternatives in the directory, then the other ways to slice it. Every count is as of the snapshot of 2026-09-22.
Snapshot of 2026-09-22 · 721 repos in the directory · every number on this page is measured against that date, not against today. What this measurement cannot tell you →