Slack alternatives — 1 repo covered

The most-starred replacement we have covered is mattermost/mattermost with 39,381 stars. Every Slack replacement, newest first. Most-starred so far: mattermost/mattermost.

From the 30-second review: “Stop paying $8/mo per seat for Slack. Mattermost does it free. This open-source team chat runs on your own servers, so every message, file, and integration stays inside your firewall — no per-seat fees, no data leaving your company. Over…”