Free, open-source alternatives to Slack
Team chat with channels. 6 apps you can run yourself instead of Slack, sorted by how well they replace it. Each one is open source, so your data stays with you.
Rocket.ChatBest match
Communications platform that puts data protection first (alternative to Gitter.im and Slack).
Zulip
Zulip is a powerful, open source group chat application.
Mattermost
Platform for secure collaboration across the entire software development lifecycle, can be integrated with Gitlab (alternative to Slack).
Element
Fully-featured Matrix client for Web, iOS & Android.
Synapse
Server for Matrix, an open standard for decentralized persistent communication.
Colanode
Collaboration suite with real-time messaging, rich text pages, file management, and dynamic databases - built for offline work (alternative to Slack, Notion).
Side by side
| App | Stars | License | Activity | Runs on |
|---|---|---|---|---|
| Rocket.Chat | 46,248 | MIT | Node.js, Docker, Kubernetes | |
| Zulip | 26,033 | Apache-2.0 | Python | |
| Mattermost | 39,322 | ⊘ Proprietary | Go, Docker, Kubernetes | |
| Element | 13,561 | Apache-2.0 | Node.js | |
| Synapse | 4,693 | Apache-2.0 | Python, Debian packages | |
| Colanode | 5,168 | Apache-2.0 | Kubernetes, Docker |
Why replace Slack?
Slack works, but your data lives in someone else's account, the price can change at any time, and features can disappear. An open-source app you run yourself is yours: you choose where it runs, who can see the data, and when to update.
Questions
What is the best free alternative to Slack?
Rocket.Chat is the closest open-source replacement for Slack in our list. Zulip and Mattermost are worth a look too, depending on what you need.
Can I self-host an alternative to Slack?
Yes. All 6 apps on this page are open source and can run on your own server, usually with Docker, or on a managed host that installs them for you.