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Team chat

Free Slack alternatives

Slack (Team chat with channels, threads and integrations) is a commercial product. These 3 tools do the same job and are free to use or to self-host.
Short answer: the best free alternatives to Slack are Mattermost, Rocket.Chat and Zulip. Self-hosting is free; you pay only for the server (a small VPS is about $4–6/mo). Licenses and prices checked 2026-10-01.
  1. 1
    Mattermost

    Self-hosted team messaging for developers

    Slack-style channels on your own servers, built for engineering teams.

    Open source (AGPL-3.0 (core)) ·details

  2. 2
    Rocket.Chat

    Open-source team chat you can self-host

    Self-hosted team chat with livechat and omnichannel inboxes.

    Open source (MIT (core)) ·details

  3. 3
    Zulip

    Open-source team chat organized by topic threads

    Team chat threaded by topic, which keeps busy channels readable.

    Open source (Apache-2.0) ·details

Want paid options too? See all Slack alternatives or the full free alternatives list.

FAQ

Is there a free alternative to Slack?+

Yes. Mattermost, Rocket.Chat and Zulip do the same job for free; Mattermost, Rocket.Chat and Zulip are open source.

What is the best open-source alternative to Slack?+

Mattermost, Rocket.Chat and Zulip are open source. Mattermost: Slack-style channels on your own servers, built for engineering teams.

Open source: OSI-approved license. Free to self-host: the code is public and free to run yourself, with limits in the license.