Alternatives to Slack

Team chat with threading

Zulip takes team chat and fixes its biggest problem: finding anything in a wall of messages. Instead of Slack's linear channels where conversations pile on top of each other, Zulip organizes every message into topics within streams.

Open source secure collaboration platform

Mattermost is what you deploy when your company says "we can't use Slack because compliance." It's a self-hosted team chat that looks and feels like Slack circa 2020 — channels, threads, file sharing, integrations — but your data stays on your servers. DevOps and security teams love it.

Open source Slack/Teams alternative

Rocket.Chat is self-hosted Slack with Department of Defense certifications. End-to-end encryption, air-gapped deployment, HIPAA compliance — if you need a team chat platform where data never leaves your servers, Rocket.Chat checks every security box.