Mastodon

Every Mastodon server talks to every other one, and to anything else implementing ActivityPub, which is rather the point. People follow friends and discover new ones, publishing links, pictures, text and video from a server run by someone they chose instead of a company they did not.

The feature set is what you would expect from a timeline, plus the moderation tools an operator actually needs.

• Chronological timelines: posts from the people you follow arrive in real time, in the order they were written.
• Media attachments: images and video upload and play inline, with silent video treated as an animated GIF.
• Safety and moderation: private posts, locked accounts, phrase filtering, muting, blocking, and a reporting system.
• OAuth2 and REST API: Mastodon acts as an OAuth2 provider, and REST and streaming APIs feed a rich third-party app ecosystem.

The stack is Ruby on Rails for the API and web pages, PostgreSQL as the main database, Redis and Sidekiq for caching and queueing, Node.js for the streaming API, and React with Redux for the dynamic parts of the interface.

Running an instance needs Ruby 3.3, PostgreSQL 14, Redis 7, Node 22 and FFmpeg 5.1 or newer. The repository carries Docker and Compose configurations plus setups for Heroku and Scalingo, Helm charts live in a separate repository, and a standalone installation guide covers a from-scratch server.