Pleroma is free, open-source social networking software for the fediverse. You can join an existing instance or install it on your own server. It communicates with compatible platforms such as Mastodon and Pixelfed, rather than limiting conversations to a single website.
Several interfaces are available, including the customizable Pleroma FE. Hosting your own instance means taking care of installation, maintenance and moderation. Existing communities set their own rules, and registrations may be closed or invitation-only.
Source: Product overview
