What is "gitter"

Gitter is an instant messaging and chat room system for developers and users of GitHub repositories. Gitter is provided as software-as-a-service, with a free option providing all basic features and the ability to create a single private chat room, and paid subscription options for individuals and organisations, which allows them to create arbitrary numbers of private chat rooms.

Individual chat rooms can be created for individual git repositories on GitHub. Chatroom privacy follows the privacy settings of the associated GitHub repository: thus, a chatroom for a private (i.e. members-only) GitHub repository is also private to those with access to the repository. A graphical badge linking to the chat room can then be placed in the git repository's README file, bringing it to the attention of all users and developers of the project. Users can chat in the chat rooms, or access private chat rooms for repositories they have access to, by logging in to Gitter via GitHub (which does not involve sharing the user's GitHub password with Gitter).

Gitter is similar to IRC and HipChat. Unlike IRC, and like HipChat, it automatically logs all messages in the cloud.