Mattermost is a self-hostable online chat service with file sharing, search, and integrations. It is designed as an internal chat for organizations and companies, and mostly markets itself as an open-source alternative to Slack and Microsoft Teams. Mattermost helps teams deliver high-quality software while meeting the safety, privacy, and scale requirements of IT and security teams. Mattermost's on-premises and secure SaaS deployments provide the benefits of modern communication without sacrificing privacy.