Mastodon is a free, open-source social network server based on open web protocols like ActivityPub and OStatus. The social focus of the project is a viable decentralized alternative to commercial social media silos that returns the control of the content distribution channels to the people. The technical focus of the project is a good user interface, a clean REST API for 3rd party apps and robust anti-abuse tools. Ruby on Rails is used for the back-end, while React.js and Redux are used for the dynamic front-end. A static front-end for public resources (profiles and statuses) is also provided.