Open-source alternatives to Microsoft Teams

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.