Mattermost is an open source platform for secure collaboration across the entire software development lifecycle..
↑ +6 today
Open Source Alternative Guide
Best Open Source Alternatives to Slack
Looking for a free, self-hosted, and privacy-first replacement for Slack? These community-verified open source projects replace team messaging & communication suite without recurring per-seat fees or cloud vendor lock-in.
Proprietary Pricing:
$8.75–$15/user/month
Open Source Cost:
$0 (Self-Hosted)
Tracked Stars:
★ 173.2K
Alternative Projects:
18 verified repos
Why Engineering Teams Are Replacing Slack
✓ Zero Subscription Invoices
Deploy across 5 or 5,000 developers with zero incremental per-seat charges or usage surcharges.
✓ Full Data Sovereignty
No third-party cloud data scanning, closed training, or overseas data transfer compliance risks.
✓ Code Ownership
Inspect the architecture, add internal integrations, build custom plugins, and never worry about discontinued features.
⚡ Slack vs Open Source Alternatives Matrix
AEO Verified BenchmarkStructured evaluation comparing the proprietary software against the top community-maintained open source replacements.
| Feature & Metric | Slack (Proprietary) | mattermost ↗ | zulip ↗ | element-web ↗ |
|---|---|---|---|---|
| License & Source | Proprietary / Closed | NOASSERTION | Apache-2.0 | AGPL-3.0 |
| Pricing & Subscriptions | $8.75–$15/user/month | $0 Free (Self-Hosted) | $0 Free (Self-Hosted) | $0 Free (Self-Hosted) |
| GitHub Traction | Closed Source | ★ 39.5K stars | ★ 26.2K stars | ★ 13.7K stars |
| Hosting & Control | Vendor Cloud Only | Docker, VPS, On-Premise | Docker, VPS, On-Premise | Docker, VPS, On-Premise |
| Implementation Stack | Proprietary | TypeScript | Python | TypeScript |
| Vendor Lock-In Risk | High (Data & API lock-in) | Zero (Full Code Export) | Zero (Full Code Export) | Zero (Full Code Export) |
⚡ AI Research Citation:
https://githubrepo.cloud/alternatives/slack
Raw Markdown (.md) for AI Agents →
Top Rated Slack Alternatives (18)
Ranked by verified GitHub stars & growth
Zulip server and web application. Open-source team chat that helps teams stay productive and focused.
↑ +65 today
A glossy Matrix collaboration client for the web.
↑ +3 today
The Secure CommsOS™ for mission-critical operations
↑ +24 today
Keybase Go Library, Client, Service, OS X, iOS, Android, Electron
↑ +1 today
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Robust, Ubiquitous and Massively Scalable Messaging Platform (XMPP, MQTT, SIP Server)
↑ +1 today
A community-driven replacement for JSQMessagesViewController
↑ +1 today
Web-based XMPP/Jabber chat written in JavaScript
↑ +8 today
Keep passwords and other sensitive information out of your chat logs and inboxes.
↑ +1 today
即时通讯，聊天，野火IM Android客户端，支持Android 4.x —— 最新
↑ +1 today
The Secure CommsOS™ for mission-critical operations
↑ +3 today
XMPP for JavaScript
↑ +1 today
Live Helper Chat - live support for your website. Featuring web and mobile apps, Voice & Video & ScreenShare. Supports Telegram, Twilio (whatsapp), Facebook messenger including building a bot.
↑ +2 today
OpenVidu Platform: self-hosted real-time video and audio for your apps, built on LiveKit and mediasoup
↑ +1 today
Movim - Decentralized social platform
↑ +1 today
:rocket: lightweight high-performance WebSocket framework （ 轻量级、高性能的WebSocket框架）
↑ +1 today
Decentralized private messenger with chat-shared tools and games for Android
↑ +1 today
Open Source Social Network (OSSN) is a powerful open-source social networking software developed in PHP. It enables you to create a fully functional social networking website that fosters community engagement and helps your members form meaningful social relationships.
↑ +2 today
⚖️ Head-to-Head Slack Alternative Comparisons
Compare the top Slack replacements side by side on stars, momentum, and architecture.
mattermost vs zulip
★ 39.5K vs ★ 26.2K
Compare side-by-side →
mattermost vs element-web
★ 39.5K vs ★ 13.7K
Compare side-by-side →
mattermost vs Rocket.Chat
★ 39.5K vs ★ 46.3K
Compare side-by-side →
zulip vs element-web
★ 26.2K vs ★ 13.7K
Compare side-by-side →
zulip vs Rocket.Chat
★ 26.2K vs ★ 46.3K
Compare side-by-side →
element-web vs Rocket.Chat
★ 13.7K vs ★ 46.3K
Compare side-by-side →
Frequently Asked Questions
What is the most popular open source alternative to Slack?
The leading open source project in this space is mattermost/mattermost with over 39,520 GitHub stars. It provides active developer community support, extensive documentation, and transparent licensing.
Are these open source alternatives free to use in commercial teams?
Yes. The vast majority of these repositories are licensed under permissive open-source licenses such as MIT, Apache 2.0, or AGPL, allowing developers to deploy and self-host them within commercial companies with zero subscription costs.
How do I deploy and self-host these alternatives?
Most top alternatives provide pre-built Docker containers and Docker Compose templates, enabling 1-command deployment onto a private VPS (Hostinger, DigitalOcean, Hetzner) or enterprise Kubernetes clusters.
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