Mattermost is an open-source collaboration platform designed for teams that need full control over their communications. It offers a secure messaging system organized into channels, with persistent history, access control, and comprehensive audit logs, all deployable on your own infrastructure rather than in a public cloud.

Beyond chat, Mattermost integrates Playbooks that transform your operational procedures into reproducible workflows, audio and video calls with screen sharing, as well as project management boards. Its rich integration capabilities and open API allow you to connect developers, their tools (CI/CD, monitoring, tickets), and their conversations in one place.

Originally designed for organizations with strict privacy requirements (government, defense sector, critical infrastructure), Mattermost is suitable for any team seeking a self-hosted alternative to Slack or Microsoft Teams, with on-premise, private cloud, or hybrid deployment, and GDPR compliance.