What is the Fediverse?

The Fediverse (a portmanteau of "federation" and "universe") is a network of interconnected, independently-operated social media servers that can communicate with each other. Unlike traditional social networks where a single company controls everything, the Fediverse is decentralized — anyone can run their own server and still interact with users on other servers.

How It Works

Each server (also called an "instance") runs software that implements the ActivityPub protocol. This protocol defines how servers:

• Discover and identify users across servers
• Send and receive posts, likes, follows, and other social activities
• Handle privacy and access control

Key Concepts

Federation

Federation means that independent servers can communicate with each other. When you post something on your Mastodon server, it can be seen by users on Pixelfed, Lemmy, or any other ActivityPub-compatible platform.

Decentralization

No single entity controls the Fediverse. Each server is independently operated with its own:

• Terms of service
• Moderation policies
• Server resources
• Community culture

Interoperability

Different software platforms can interact because they all speak the same protocol (ActivityPub). A Mastodon user can:

• Follow a Pixelfed photographer
• Comment on a PeerTube video
• Participate in a Lemmy community

The Protocol Stack

The Fediverse relies on a handful of open standards — ActivityPub and Activity Streams from the W3C, WebFinger (IETF RFC 7033), and HTTP Signatures. Most servers still sign with an older IETF draft (draft-cavage-http-signatures); its standardized successor, RFC 9421, is being adopted alongside it (details):

Protocol	Purpose
ActivityPub	Federation protocol for social networking
ActivityStreams 2.0	JSON format for representing social data
WebFinger	User discovery across servers
HTTP Signatures	Message authentication

Popular Fediverse Platforms

Platform	Type	Description
Mastodon	Microblogging	Twitter-like platform, most popular
Lemmy	Link aggregation	Reddit-like communities
Pixelfed	Photo sharing	Instagram-like experience
PeerTube	Video hosting	YouTube alternative
Misskey	Microblogging	Feature-rich Japanese platform
Pleroma	Microblogging	Lightweight alternative to Mastodon
GoToSocial	Microblogging	Privacy-focused, lightweight
Friendica	Social network	Facebook-like features

Why Build for the Fediverse?

For Users

• Choice of server: Users can pick a server whose rules suit them, move to another, or self-host
• Timelines: Most microblogging servers show the home timeline in chronological order
• Community-driven moderation: Each server sets its own rules
• No single owner: No one company controls the network, its data or its ranking

For Developers

• Open standards: Build on W3C recommendations
• Interoperability: Your software works with the entire ecosystem
• Less platform lock-in: Users can move accounts and take their followers with them (posts don't move automatically — see Account Migration)
• Growing ecosystem: Millions of users, thousands of servers

Scale of the Fediverse

As of October 2026, FediDB counts:

• About 14 million registered accounts, of which about 1.34 million were active in the last month
• Roughly 36,000–42,000 servers (FediDB's server count varies from day to day as servers come and go)
• Hundreds of different software implementations

These are lower bounds: FediDB only counts servers it can discover, and not every server publishes user counts.

Next Steps

Ready to start building? Here's your path:

1. Core Concepts - Understand Actors, Activities, and Objects
2. Your First ActivityPub Server - Build a minimal implementation
3. Understanding Federation - Learn how servers communicate

External Resources

• ActivityPub Specification (W3C)
• Fediverse.info - User-friendly introduction
• FediDB - Fediverse statistics