Gitter

Gitter is an open-source instant messaging and chat room system for developers designed to make community messaging, collaboration and discovery as smooth and simple as possible. Gitter is provided as software-as-a-service and integrates with GitLab and GitHub repositories to make discussion around code even easier. With Gitter, you can can easily create, organise and grow your communities, inviting others to join just in one click. Over 1.5M users across 100K communities use Gitter to discuss code and development progress.