The word Fediverse is a blend (or portmanteau) of the words federated and universe. Universe of what? Of apps (social networks, blogs, cloud services, etc.). Federated with whom? The apps with each other. In practice, the Fediverse is a collection of different apps that can interact with each other (because, well, they’re federated). Imagine a Facebook user being able to interact with YouTube—like leaving comments—without needing a YouTube account. This interaction is possible because each of these apps adopts (and builds upon) a communication protocol called ActivityPub. All these apps are open source and can be installed by anyone with the technical skills and resources (servers and software suited to the app). The fact that anyone can install their own version means that for each app, there are multiple installations—called instances—that users can join. All these different instances are connected to each other and to other apps via the ActivityPub protocol.

You might ask: How can a user join one of these apps if they don’t have the technical skills to set up their own instance? The answer is simple: after choosing the app they’re interested in, they can pick the instance that best suits them.

But what does it mean to “choose” an instance? Why pick one over another? Aren’t they all the same? If you sign up for Instagram, for example, you don’t get to choose an instance (or server)… but the Fediverse is decentralized, so the servers running an app—even if they use the same software and features—each have their own specific rules and sometimes themes. For example, there are social network instances (like Mastodon) dedicated only to gaming or books. Users can choose based on their interests and the rules they’re willing to follow.

Once they’ve chosen an instance, they can sign up by providing an email, picking a username, and setting a password. No other data is required because the Fediverse doesn’t rely on user data—there’s no profiling algorithm, and instances aren’t interested in collecting more data than necessary to run the apps.

Now there’s only one question left: Why aren’t you registered yet?