Open-source alternatives to Slack

1

Rocket.Chat

Self-hosted team messaging — channels, video, and compliance.

MIT-licensed alternative to Slack and Mattermost with end-to-end encryption, Omnichannel, an apps marketplace, and FedRAMP-ready compliance.

Pricing: Free and self-hosted (MIT); paid Enterprise/Cloud tiers add omnichannel support and SLAs.

• Closest feature parity with Slack
• Large marketplace of apps and integrations
• Self-hosting requires more ops effort than Slack's SaaS
• Some enterprise features are gated behind a paid tier

2

Mattermost

Secure team collaboration — messaging, playbooks, and integrations.

MIT-licensed alternative to Slack with channels, threads, webhooks, Jira/GitHub integrations, and Playbooks for incident response. Desktop and mobile apps included.

Pricing: Free and self-hosted (MIT); paid Enterprise and Cloud tiers add SSO and compliance features.

• Strong DevOps integrations (Jira, GitHub, webhooks)
• Playbooks feature built for incident response
• UI feels less polished than Slack
• Some compliance features require the paid tier

3

Huly

Collaborative workspace combining chat, projects, docs, and planning.

Huly is an EPL-2.0 workspace with team chat, project management, collaborative documents, GitHub integration, planning, audio/video, and a virtual office.

Pricing: Free and self-hostable under EPL-2.0; hosted services may be offered separately.

• Chat, projects, documents, and planning
• GitHub integration
• Self-hosted unified workspace
• Broader than Slack
• More infrastructure to operate
• Younger ecosystem

4

Zulip

Topic-threaded team chat — keeps conversations organized at scale.

Zulip is an open-source team chat application built around topic-based threading, which keeps conversations organized in a way that channel-only tools like Slack don't. Apache-2.0 licensed.

Pricing: Free and open source, self-hosted; also offers a hosted Zulip Cloud plan.

• Topic threading scales better for large, busy teams
• Fully open source, no paid-tier feature gating
• Topic-based model has a learning curve versus flat channels
• Smaller app/integration ecosystem than Slack

5

Element

Matrix-based team messaging — decentralized and end-to-end encrypted.

Element is an open-source, end-to-end encrypted collaboration client built on the decentralized Matrix protocol, so it can federate across independent servers rather than relying on one company's infrastructure.

Pricing: Free and self-hosted (AGPL-3.0); Element also sells hosted plans and enterprise support.

• Decentralized Matrix protocol avoids vendor lock-in
• End-to-end encryption by default
• Federation adds operational complexity
• Interface is less streamlined than centralized tools

6

Fluxer

Discord-style chat for communities — messaging, voice, and video, self-hostable.

Fluxer is a free, open-source instant messaging and VoIP platform for friends, groups, and communities, styled after Discord. AGPL-3.0 licensed with self-hosting support.

Pricing: Free and open source (AGPL-3.0), self-hosted.

• Discord-style UX familiar to many users
• Voice and video included
• Younger project, smaller community
• Fewer business-focused integrations than Slack

7

Campfire

Simple self-hosted group chat from 37signals — one-time, MIT-licensed, no subscription.

Campfire is a simple, self-hosted group chat application from 37signals, released as open source under the MIT license in 2025. It's deliberately minimal — @mentions, DMs, rooms — with no recurring subscription.

Pricing: One-time source-code purchase from 37signals, no subscription; self-hosted only.

• No recurring subscription cost
• Extremely simple, low operational overhead
• Minimal feature set — no threads, no video calls
• Not designed to scale to large organizations

8

Cinny

Elegant Matrix client — end-to-end encrypted, clean interface.

Cinny is an open-source Matrix client focused on a simple, elegant interface for end-to-end encrypted conversations. AGPL-3.0 licensed, it connects to any Matrix homeserver.

Pricing: Free and open source (AGPL-3.0), self-hosted; requires a separate Matrix homeserver.

• Clean, focused interface
• Full Matrix end-to-end encryption
• Requires running or connecting to a Matrix homeserver separately
• Fewer built-in integrations than Slack

9

Stoat

Self-hostable Discord alternative (formerly Revolt) — servers, channels, voice.

Stoat (formerly Revolt) is an open-source, self-hostable group chat platform styled after Discord — servers, channels, voice, and moderation — built in the EU with no ads or data mining.

Pricing: Free and open source (AGPL-3.0), self-hosted.

• Discord-style UX, EU-based with no ad tracking
• Active development
• Smaller community than established options
• Less mature for business or compliance use cases

10

Wire

End-to-end encrypted team collaboration — messaging, calls, EU-based.

Wire is an open-source, end-to-end encrypted collaboration platform for messaging, calls, and file sharing, aimed at organizations with strong security and compliance requirements. AGPL-3.0 licensed.

Pricing: Free and self-hosted (AGPL-3.0) via wire-server; Wire also sells hosted enterprise plans.

• Strong compliance and security track record, EU-based
• End-to-end encrypted calls and messaging
• Self-hosting wire-server is notably complex (many services)
• Smaller community than Rocket.Chat or Mattermost

11

Quiet

Peer-to-peer team chat over Tor — no servers, no phone number, no metadata.

Quiet is an open-source, peer-to-peer team chat that syncs messages directly between devices over Tor, with no central server, no phone number, and no metadata collection. GPL-3.0 licensed.

Pricing: Free and open source (GPL-3.0). No server to host.

• No server to host or maintain — fully peer-to-peer
• Maximum privacy: no phone number, no metadata
• No central history or backup if all devices are offline
• Not designed for large teams or enterprise use

12

Twake Chat

Federated Matrix messenger for teams and organizations.

Twake Chat is an AGPL-3.0 Matrix-based messenger with encrypted messaging, federation, bridges, multi-device sync, video conferencing, and on-premises deployment.

Pricing: Open-source components are self-hostable; verify current additional terms and hosted options.

• Matrix federation and E2EE
• Bridges, SSO, and video conferencing
• European on-premises ecosystem
• Matrix infrastructure can be complex
• Smaller ecosystem than Element
• Different UX from Slack

13

Buzz

AI-native team workspace for humans and coding agents.

Buzz is an Apache-2.0 workspace combining team chat, project planning, Git workflows, shared context, and autonomous AI agents participating directly in conversations.

Pricing: Free and self-hostable under Apache-2.0; verify current hosted terms.

• AI agents as collaborators
• Team chat and Git workflows
• Shared human/AI context
• Very young
• Developer-oriented
• Smaller ecosystem

14

Nextcloud Talk

Self-hosted chat, calls, video, and screen sharing in Nextcloud.

Nextcloud Talk is an AGPL-3.0 communication component providing chat, voice/video calls, screen sharing, file collaboration, federation, and integration with Nextcloud Files, Calendar, and Contacts.

Pricing: Free and self-hostable as part of Nextcloud; enterprise support may be paid.

• Chat, voice, video, and screen sharing
• Deep Nextcloud integration
• Federation and on-premises deployment
• Best with an existing Nextcloud deployment
• Larger infrastructure footprint
• Less chat-focused than Slack

15

Colanode

Local-first workspace for chat, documents, databases, and files.

Colanode is an Apache-2.0 local-first collaborative workspace combining team chat, direct messages, rich documents, databases, files, and CRDT synchronization.

Pricing: Free and self-hostable under Apache-2.0; verify current hosting options.

• Chat, pages, databases, and files
• Local-first architecture
• CRDT synchronization and self-hosting
• Broader than Slack
• Younger ecosystem
• Different workflow from traditional SaaS chat

16

Mezon

Open community communication with channels, voice, video, and bots.

Mezon is an MIT communication platform combining channels, voice, video, bots, integrations, cross-platform applications, and real-time community features.

Pricing: Free and open source under MIT; deployment and hosted terms may vary.

• MIT licensed
• Channels, voice, video, bots, and APIs
• Cross-platform community features
• More community-oriented
• Smaller business integration ecosystem
• Younger platform

17

Valour

Customizable open-source community messaging with federation.

Valour is an AGPL-3.0 community communication platform offering channels, multi-window chat, self-hosting, federation, bots, APIs, and customization.

Pricing: Free and self-hostable under AGPL-3.0; verify current deployment options.

• Federation and self-hosting
• Channels, bots, and API
• Community-driven customization
• More community than workplace focused
• Small ecosystem
• Limited enterprise governance

18

SAMA

Self-hosted messaging infrastructure for custom communication products.

SAMA is a GPL-3.0 messaging server with private and group chats, encryption, presence, read receipts, attachments, notifications, user management, and clustering.

Pricing: Free and self-hostable under GPL-3.0; client development and infrastructure costs apply.

• Messaging APIs and realtime primitives
• Encryption, presence, and push notifications
• Clustering and multi-device support
• Not a ready-to-use Slack workspace
• Requires application development
• Smaller ecosystem