Open-source alternatives to Slack
The most popular self-hosted, open-source alternatives to Slack (team chat) are Rocket.Chat (46,288 GitHub stars), Mattermost (39,373 GitHub stars) and Zulip (26,067 GitHub stars). SelfHostHub lists 12 options below, taken from its Custom Communication Systems category; 6 support Docker and all of them can run on your own server.
Comparison of self-hosted Slack alternatives
| Project | GitHub stars | Licence | Language / platform | What it does |
|---|---|---|---|---|
| Rocket.Chat | 46,288 | MIT | Nodejs, Docker, K8S | Communications platform that puts data protection first (alternative to Gitter.im and Slack). |
| Mattermost | 39,373 | ⊘ Proprietary | Go, Docker, K8S | Platform for secure collaboration across the entire software development lifecycle, can be integrated with Gitlab (alternative to Slack). |
| Zulip | 26,067 | Apache-2.0 | Python | Zulip is a powerful, open source group chat application. |
| SimpleX Chat | 19,580 | AGPL-3.0 | Haskell | The most private and secure chat and applications platform - now with double ratchet E2E encryption. |
| OpenWA | 15,553 | MIT | Docker | WhatsApp API gateway exposing messaging as REST endpoints, with a web dashboard, multi-account sessions, and webhook events (alternative to WhatsApp Business API providers). |
| Tinode | 13,528 | GPL-3.0 | Go | Instant messaging platform. Backend in Go. Clients: Swift iOS, Java Android, JS webapp, scriptable command line; chatbots. |
| Centrifugo | 10,883 | MIT | Go, Docker, K8S | Language-agnostic real-time messaging (Websocket or SockJS) server. |
| Fluxer | 10,614 | AGPL-3.0 | Docker | Instant messaging and VoIP platform built for friends, groups, and communities (alternative to Discord). |
| Mumble | 8,348 | BSD-3-Clause | C++, deb | Low-latency, high quality voice/text chat software. |
| Tox | 2,695 | GPL-3.0 | C | Distributed, secure messenger with audio and video chat capabilities. |
| Stoat | 2,678 | AGPL-3.0, MIT | Rust | Stoat is a user-first chat platform built with modern web technologies. |
| Tuwunel | 2,646 | Apache-2.0 | deb, Docker, Nix, Rust | High-performance and feature-rich chat server for Matrix, and the successor to conduwuit (fork of Conduit). |
Star counts and licences come from the awesome-selfhosted dataset and may lag GitHub slightly.
Browse the full categories
All self-hosted Communication - Custom Communication Systems
Frequently asked questions
What is the best open-source alternative to Slack?
By GitHub stars, Rocket.Chat is the most popular self-hosted alternative to Slack listed here, followed by Mattermost and Zulip. The best fit depends on the features and stack you need.
Is there a free self-hosted alternative to Slack?
Yes. All 12 projects on this page are open source and can be self-hosted at no licence cost; you pay only for your own server.
Which licences do these Slack alternatives use?
The most common licences among them are MIT (4), AGPL-3.0 (3) and Apache-2.0 (2).
Can I run a Slack alternative with Docker?
6 of the 12 alternatives list Docker as a supported platform.