Open-source team chat
Replacing: Slack
| Project | What it is | Stars | Last release | Replaces |
|---|---|---|---|---|
| Rocket.Chat Active Mixed or custom | A team chat platform with channels, direct messages, video calls and integrations that you can host yourself. | 46.3k | Oct 28, 2026 | Slack |
| Mattermost Active Mixed or custom | Mattermost is an open source platform for secure collaboration across the entire software development lifecycle. | 39.5k | Oct 28, 2026 | Slack |
| Zulip Active Apache-2.0 | Zulip server and web application. Open-source team chat that helps teams stay productive and focused. | 26.1k | Sep 21, 2026 | Slack |
| Element Active AGPL-3.0 | Element, a chat app for the Matrix network, with end-to-end encrypted rooms and calls. | 13.6k | Oct 27, 2026 | Slack |