Zulip server and web application. Open-source team chat that helps teams stay productive and focused.
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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:
★ 58.6K
Alternative Projects:
17 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.
Top Rated Slack Alternatives (17)
Ranked by verified GitHub stars & growth
A glossy Matrix collaboration client for the web.
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Macro is a unified workspace for teams: email, chat, docs, tasks, agents, calls, and CRM — @-linked together with shared AI memory.
↑ +23 today
PipesHub is an open-source platform for securely connecting enterprise knowledge to AI. Give AI agents trusted context and your team permission-aware search with verified citations across your business systems.
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Next generation noIM application in your own workspace, not only another Slack/Discord/Rocket.chat
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❤️ Fredy - [F]ind [R]eal [E]state [D]amn Eas[y] - Fredy keeps searching for new apartments, houses, and flats in Europe on platforms like ImmoScout24, Immowelt, eBay Kleinanzeigen and instantly delivers the results to you via Slack, Telegram, Email, Discord or ntfy, so you can focus on the more important things in life ;)
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:eyes: monitor & detect crashes in your Kubernetes(K8s) cluster instantly
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Your Company Agentic Operating System
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Open-sourcing our company brain - A teammate in your Slack that remembers everything your team says, and can go do the work.
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Push notification SDK(AnPush、Bark、Chanify、DingTalk、Discord、Gitter、GoogleChat、IGot、Lark、Mattermost、MicrosoftTeams、NowPush、Ntfy、Push、Pushback、PushBullet、PushDeer、PushMe、Pushover、PushPlus、QQ、RocketChat、ServerChan、ShowdocPush、SimplePush、Slack、Telegram、WeWork、WPush、XiZhi、YiFengChuanHua、ZohoCliq、Zulip).
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The local-first Agent OS — your AI partner lives on your own machine. Drive the official Claude Code, Codex & OpenCode from your browser or any chat app.
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Business operating system for Claude Code — 57 skills, 21 agents, smart daemon. Unified inbox (WhatsApp/Email/Slack/Telegram), autonomous PR merge, full-AWS monitoring, revenue (Stripe+RevenueCat), e-commerce (Shopify), marketing (Klaviyo/Meta/GA4), voice (Bland/ElevenLabs), APM (Datadog/NewRelic/OTEL), YOLO mode.
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Affordable notifications for Kubernetes
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Astra is a structured log search and analytics engine developed by Slack and Salesforce
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Open-source control plane and runtime for organisational agents: shared company context & brain
↑ +1 today
Slack CLI for humans and AI agents. Read, send, search and reply across one or many Slack workspaces from the terminal. No Slack app needed.
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Frequently Asked Questions
What is the most popular open source alternative to Slack?
The leading open source project in this space is zulip/zulip with over 25,951 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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