Mattermost is an open-source, self-hosted online chat service, with the ability to support both direct messaging and group chats. Its primary function is to offer teams a way to communicate and collaborate in a unified workspace. Modeled to compete with the likes of Slack and Microsoft Teams, Mattermost aims to provide similar functionality while giving users complete control over their data and privacy.

Launched in 2015 by Mattermost Inc., the platform was designed to be extensible and customizable to suit various user needs. One of its strengths lies in the ability to integrate with other popular developer tools such as Jira, Jenkins, GitLab, and many more. This integration capability allows teams to streamline their workflows and improve overall productivity. Mattermost is available in two versions. The Team Edition is the open-source version that includes core features and functionalities. On the other hand, the Enterprise Edition, a commercial version, provides additional features such as advanced user management, enhanced security, and scalability options designed for large organizations.