The best open source alternative to Slack is Element. It's not free, so if you're looking for a free alternative, you could try Element or Zulip. If that doesn't suit you, our users have ranked more than 100 alternatives to Slack and loads of them is open source so hopefully you can find a suitable replacement. Other interesting open source alternatives to Slack are Matrix, Wire, Stoat Chat and Threema.
Self-hostable open-source chat solution offering text, voice, and video with fine-grained roles, forum threads, DM workspace, browser soundboard, custom emoji, PWA offline support, push notifications, analytics tools, and advanced moderation capabilities.
Prose is a distributed, open-source, and native platform for workplace communication.
This simple Matrix client written in Python allows you to send and receive messages and files, verify other devices, and interact with your Matrix account or other Matrix users in many ways. You use it from the terminal (CLI) or integrate it into other simple Python programs.
PeerSuite is an open source, decentralized, private alternative to apps like Discord or Slack. All data is sent only between clients through encrypted WebRTC channels.
End-to-end encrypted chat, VOIP, and video calling used by millions of people.
Fast open source Slack desktop app, written in Node.js with native UI powered by the Yue library.
An IRC-like internet chatroom hosted on ZeroNet, a distributed network. 0rc is a fully distributed website, and messages are shared through peers using the ZeroNet stack. In addition, making a new chatroom website is a simple as downloading the files and cloning the site.
Glowing Bear is a sleek, modern web frontend that securely connects to a running instance of WeeChat using its built-in relay protocol. It relies on WeeChat to do all the heavy lifting and then provides some nice features on top of that, like...
Start your next video call with a single click. No download, plug-in or login required. Just get straight to talking, messaging and sharing your screen.
Dirc is a peer-to-peer web application which uses WebRTC to set up connections between chat participants without requiring a back-end server. The static files can be self-hosted. Other features:
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