Rocket.Chat
Self-hosted team messaging — channels, video, and compliance.
MIT-licensed alternative to Slack and Mattermost with end-to-end encryption, Omnichannel, apps marketplace, and FedRAMP-ready compliance.
Mattermost
Secure team collaboration — messaging, playbooks, and integrations.
MIT-licensed alternative to Slack with channels, threads, webhooks, Jira/GitHub integrations, and Playbooks for incident response. Desktop and mobile apps.
Zulip
Topic-threaded team chat — keeps conversations organized at scale.
Zulip is an open-source team chat application built around topic-based threading, which keeps conversations organized in a way that channel-only tools like Slack or Rocket.Chat don't. Apache-2.0 licensed and self-hostable.
Element
Matrix-based team messaging — decentralized and end-to-end encrypted.
Element is an open-source, end-to-end encrypted collaboration client built on the decentralized Matrix protocol, so it can federate across independent servers rather than relying on one company's infrastructure. AGPL-3.0 licensed.
Wire
End-to-end encrypted team collaboration — messaging, calls, EU-based.
Wire is an open-source, end-to-end encrypted collaboration platform for messaging, calls, and file sharing, aimed at organizations with strong security and compliance requirements. AGPL-3.0 licensed, based in the EU.
Compare Microsoft Teams alternatives
| Tool | Stars | Forks | License | Self-hosted |
|---|---|---|---|---|
| Rocket.Chat | 45.4K | 13.6K | MIT | Yes |
| Mattermost | 36.9K | 8.7K | MIT | Yes |
| Zulip | 25.5K | 9.9K | Apache-2.0 | Yes |
| Element | 13.3K | 2.7K | AGPL-3.0 | Yes |
| Wire | 2.8K | 333 | AGPL-3.0 | Yes |
Microsoft Teams is Microsoft's proprietary team chat and video platform, bundled into Microsoft 365 subscriptions. It's closed source and tightly coupled to the Microsoft 365 ecosystem, which can be a downside if you want a standalone tool or need to keep chat data on infrastructure you control.
Rocket.Chat and Mattermost are both open-source, self-hostable team messaging platforms that don't require a Microsoft 365 subscription.
FAQ
Is there a free, open-source alternative to Microsoft Teams?
Yes. Rocket.Chat and Mattermost are both open source (MIT) and free to self-host.
What's the best open-source alternative to Microsoft Teams?
Rocket.Chat leans toward broader omnichannel and compliance features. Mattermost leans toward developer-focused workflows with playbooks and deeper DevOps integrations.
What are the top open-source alternatives to Microsoft Teams?
Browse all open-source alternatives to Microsoft Teams above, or explore the full Communication & Community category for more options.