Rocket.Chat
Self-hosted team messaging with voice, video, and AI
May 201546.3k+146–updated today
R.I.P.Open-source alternatives to Slack
17 projects replace Slack, the team chat. 15 shipped code in the last 30 days.
Slack charges per active user. On the free plan, messages older than 90 days are hidden, and since 2024 Slack deletes free workspace data older than a year. Some teams also need chat records on servers they control for legal or security reasons.
Mattermost and Rocket.Chat are the usual company picks, with channels, threads, integrations and a Slack import. Zulip puts every conversation under a topic, which works well for teams across time zones who read chat in batches. Element runs on Matrix, so separate organizations can talk to each other without sharing one server.
17 shown
Mattermost
Secure collaboration platform for mission-critical work
Jun 201539.4k+265–updated today
Buzz
Team chat, project management, and AI agents in one place
Mar 202636.2k+2.4kApache-2.0updated today
Huly
All-in-one workspace for project, chat, and docs
Aug 202127.9k+201EPL-2.0updated 1d ago
Zulip
Organized team chat for distributed teams
Sep 201526.1k+147Apache-2.0updated today
Element
Secure, decentralized messaging for teams and individuals
Jul 201513.6k+116AGPL-3.0updated today
Fluxer
Open source messaging with privacy and community focus
Jan 202610.6k+294AGPL-3.0updated today
Colanode
Self-hosted team workspace with chat, docs, and databases
Jul 20245.2k+26Apache-2.0updated 6mo ago
Campfire
Self-hosted group chat without recurring subscription fees
Aug 20254.8k+153MITupdated today
Cinny
Secure and elegant Matrix client for seamless conversations
Apr 20213.9k+39AGPL-3.0updated 1d ago
Stoat
Group chat for friends and communities, without the baggage
Jun 20213.4k+71–updated today
Quiet
Serverless team chat over Tor, no phone number needed
Dec 20212.7k+12GPL-3.0updated 1d ago
Wire
Secure collaboration platform with end-to-end encryption
Mar 20162.6k+6GPL-3.0updated 9mo ago
Mezon
Create custom spaces to chat, game, and connect globally
Jan 20242k+229–updated today
Valour
Community-driven platform built for transparency
Oct 2020400+2AGPL-3.0updated today
Twake Chat
Secure open source messaging for professional teams
Mar 2023171+5AGPL-3.0updated today
SAMA
Secure, scalable chat server for modern applications
Sep 2022161+3GPL-3.0updated 15d ago
What you give up by leaving Slack
The honest part. Free and open usually costs something else.
- Fewer ready apps Slack's directory has thousands of apps; alternatives support webhooks and bots, but far fewer ready connections.
- Partners stay on Slack Shared channels with clients and vendors depend on everyone using Slack, and that network does not follow you.
- Calls vary Built-in audio and video calls differ a lot between projects and often need extra servers.
- Ops are on you Chat for a whole company means monitoring, backups and mobile push setup that Slack handled for you.
