Mattermost Team Chat

Mattermost is an open-source, self-hostable team messaging platform created by Ian Tien in 2015, headquartered in Palo Alto, providing real-time messaging, channels, direct messages, threads, file sharing, search, integrations, webhooks, bots, and workflow automation as a secure alternative to Slack for organizations with data sovereignty and compliance requirements, available as Team Edition for free and Enterprise Edition for advanced features, adopted by government agencies, financial institutions, and defense organizations including the United States Department of Defense and Nasdaq for their internal communications. The messaging system organizes conversations into channels including public channels visible to all team members, private channels restricted to invited members, and direct messages for one-on-one communication, with each message supporting rich text formatting through Markdown, code blocks with syntax highlighting, file attachments, reactions, mentions, and threading. The integration framework provides incoming webhooks for posting messages from external systems, outgoing webhooks for triggering actions, slash commands for custom interactions, REST API for programmatic access, and bot accounts for automated responses, with pre-built integrations for over seven hundred applications including Jira, GitHub, GitLab, and PagerDuty through the marketplace. The enterprise features include compliance reporting, data retention policies, active directory and LDAP integration, SAML single sign-on, and multi-factor authentication. The mobile and desktop apps. The high availability. The cluster mode. Designed by Ian Tien. Designed for enterprise teams.