Open Source Team Chat & Messaging Tools using CSS
A curated collection of the best open source platforms for real-time team messaging, with channels, direct messages, threads, file sharing, and app integrations. using CSS.
Team chat with email, tasks, and docs in one workspace
Stars
Stars growing over the last 30 days4,771Last commit
8 hours agoLicense
AGPL-3.0
Team chat app with inline threads, mention-based sharing, a unified inbox for chat and email, and an AI agent that works across your full workspace.
Open Source Alternative to:
Team chat, project management, and AI agents in one place
Stars
Stars growing over the last 30 days36,168Last commit
11 hours agoLicense
Apache-2.0
Workspace that combines team chat, project planning, and git management with AI agents that collaborate alongside your team on shared context.
Open Source Alternative to:
Self-hosted team messaging with voice, video, and AI
Stars
46,294Last commit
7 hours agoLicense
MIT
Open source communication platform combining messaging, voice, video, and AI for organizations that need full data control, air-gapped deployments, and zero-trust security.
Open Source Alternative to:
Secure collaboration platform for mission-critical work
Stars
39,384Last commit
6 hours agoLicense
Unknown
Mattermost provides a flexible, open-source platform for secure team collaboration, designed for organizations with strict security and privacy requirements.
Open Source Alternative to:
Organized team chat for distributed teams
Stars
26,080Last commit
11 hours agoLicense
Apache-2.0
Zulip is an open-source team chat app that uses threaded conversations to keep communication organized and efficient for teams of all sizes.
Open Source Alternative to:
Open source messaging with privacy and community focus
Stars
10,620Last commit
1 day agoLicense
AGPL-3.0
Free, open-source instant messaging and VoIP platform with full Markdown support, voice/video calls, moderation tools, and self-hosting options for communities.
Open Source Alternative to:
Secure, decentralized messaging for teams and individuals
Stars
13,600Last commit
18 hours agoLicense
AGPL-3.0
Open-source platform for encrypted communication, file sharing, and collaboration based on the Matrix protocol.
Open Source Alternative to:
Self-hosted group chat without recurring subscription fees
Stars
Stars growing over the last 30 days4,791Last commit
15 hours agoLicense
MIT
Install your own group chat system with @mentions, DMs, and mobile support. One-time purchase, no monthly fees. Includes full source code for customization.
Open Source Alternative to:
Secure and elegant Matrix client for seamless conversations
Stars
3,937Last commit
18 hours agoLicense
AGPL-3.0
Cinny offers a simple, elegant, and secure interface for Matrix-based conversations, protected by end-to-end encryption.
Open Source Alternative to:
Create custom spaces to chat, game, and connect globally
Stars
Stars growing quickly over the last 30 days2,008Last commit
6 hours agoLicense
MIT
Build your own community space for gaming, chatting, and hanging out with friends worldwide. Customize your environment for the perfect social experience.
Open Source Alternative to:
Transform team email into efficient collaborative workflows
Stars
1,760Last commit
8 months agoLicense
AGPL-3.0
Streamline team communication with shared inboxes, unlimited email addresses, and customizable workflows. Perfect for modern businesses seeking organized email management.
Open Source Alternative to:
Secure open source messaging for professional teams
Stars
Stars growing over the last 30 days171Last commit
6 hours agoLicense
AGPL-3.0
Free Matrix-based messenger with end-to-end encryption, multi-platform bridges, and on-premise deployment. Connect across 30+ networks securely.
Open Source Alternative to:
c15t – Open-source cookie banner, built for control and lightening fast modern web apps.
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