SHSelfHostIndex

60 self-hosted Slack alternatives

Slack is a commercial team messaging platform organized into channels, with integrations, voice, and video. It is widely used for workplace communication. These open-source apps let you replace Slack with software you host and control yourself.

Best self-hosted Slack alternatives

Last reviewed Aug 26, 2026 · 456 words

A 20-person team on Slack's Pro plan pays about $2,100 a year at last check. The same team fits comfortably on one 2 GB virtual machine running Mattermost, with message history that never disappears behind a paywall - Slack's free tier hides everything older than 90 days, including your own words. That is the pitch. The honest counterweight: Slack's polish is real, and whoever runs the replacement inherits the "chat is down" messages, delivered by every channel except chat.

What you gain and what you give up

Gained: unlimited history and unlimited users at no per-seat cost, plus data that never leaves your network, which is why compliance-heavy shops keep landing on Mattermost. Given up: the long tail of Slack's app directory - thousands of integrations against the alternatives' dozens - along with Huddles and a level of mobile-app finish none of the replacements quite reach. One more honesty item: Mattermost and Rocket.Chat are open core, so certain SSO modes and compliance features stay behind paid licences even on your own server. And the catalogue's resource floor is uniform: 2,048 MB minimum for each of the three serious contenders.

Which replacement fits which user

Engineering teams should start with Mattermost (38,901 stars, AGPL): channels and threads that feel like Slack on day one, strong DevOps integrations, playbooks and kanban boards included. Distributed and async-heavy teams do better with Zulip (25,770 stars, Apache-2.0, fully open source), whose topic-per-thread model turns 300 unread messages into a 5-minute catch-up - after roughly a week of retraining your habits. Rocket.Chat (46,030 stars, MIT) has the widest surface, including an omnichannel customer-support inbox, and is correspondingly the heaviest to operate. Organisations that care about federating with outsiders should consider a Matrix stack, Synapse plus Element Web, accepting its Hard difficulty rating as the price of an open protocol.

Getting your history out

Slack's self-serve export is a ZIP of JSON files covering public channels only; private channels and DMs require a paid plan's corporate export. All three replacements ship importers for that ZIP, and they genuinely work - users, channels, and message history arrive. Nothing else does: every bot, app, webhook, and workflow gets rebuilt by hand. Run old and new side by side for two weeks and move teams over channel by channel.

The default pick

Mattermost, for the least retraining and the smoothest import. Switch the recommendation to Zulip the moment your team spans more than 3 time zones, because threading discipline beats polish for async work. The rest of the field lives in the team chat category.

Choosing well

How to choose Matrix/XMPP server: the Matrix & XMPP buyer's guide

Compare Slack alternatives