Mattermost is an open-source messaging and collaboration platform designed primarily for teams and organizations that need secure, self-hosted, and highly customizable communication tools—similar to Slack, but with more control and privacy.
Team Messaging (Chat)
Channels for team and topic-based communication (public/private)
Direct and group messaging
Threaded conversations
Security & Privacy
End-to-end control over data and infrastructure
Integration & Extensibility
Integrates with DevOps tools (like GitLab, Jira, Jenkins)