What is the fediverse? A plain guide for people who post

Servers, ActivityPub, and why Mastodon works the way it does — explained for someone who wants to post, not build a server.

The fediverse is a group of social networks that can talk to each other. Not one site with one company behind it, but thousands of independently run servers that pass messages back and forth using a shared standard.

That is the whole idea. Everything else — the server names in handles, the culture, the reason it feels different — follows from it.

The email comparison, and where it breaks

The usual explanation is email: your address is on one provider, mine is on another, and we can still write to each other because everyone agreed on a protocol. That is exactly right, and it is the fastest way to understand handles like @you@yourserver.social.

Where the comparison misleads is culture. Email providers are interchangeable utilities. Fediverse servers are not — they have visible admins, stated rules, distinct communities, and moderation policies that differ enormously. Which server you join genuinely shapes your experience in a way your email provider does not.

ActivityPub is the agreement

The protocol underneath is ActivityPub, a W3C standard that became a recommendation in 2018. It defines how servers tell each other that someone posted, followed, liked or replied.

Because it is a standard rather than a product, different kinds of software can implement it and interoperate. Mastodon is microblogging. PeerTube is video. Pixelfed is photos. Someone on Mastodon can follow a PeerTube channel, because both speak the same language.

What this means when you post

• Your server holds your account. Your posts live there, your admin runs it, and its rules apply to you.
• Your reach is not your server. People on other servers follow you normally. Being on a small server does not mean a small audience.
• Feeds are chronological by default. There is no engagement algorithm deciding what surfaces. Timing matters more, and outrage travels less.
• Moderation is local and opinionated. Servers block other servers. That is a feature, and it is why choosing one with a moderation policy you agree with matters.
• You can move. Migration carries your followers to a new server. It does not carry your posts, and it does not carry anything you had scheduled.

How Bluesky differs

Bluesky is decentralised too, but on a different protocol — the AT Protocol — so it is not part of the fediverse and the two cannot talk directly without a bridge.

The architectures differ in a way you can feel. ActivityPub pushes: your server delivers your post to the servers of people who follow you. AT Protocol pulls: services query a relay for events. In practice AT Protocol makes stronger portability guarantees and offers algorithmic choice, while ActivityPub gives your server's admin more say and defaults to chronological.

Neither is simply better. They are different bets about where control should sit. If you want to be on both, there are three ways to do it — and a fuller comparison of the three networks if you are still choosing.

Where Threads fits

Meta's Threads has been connecting to the fediverse over ActivityPub. Fediverse users can follow Threads accounts that have opted in, and replies from Mastodon can appear back on Threads.

It is partial and it is deliberately walled off — fediverse content sits outside the main ranked feed rather than mixed into it. The asymmetry is also real: Meta operates at a scale that dwarfs the rest of the network, which is why the integration is welcomed by some fediverse admins and blocked outright by others.

Picking a server

The advice people give is to pick a server matching your interests. Reasonable, and slightly overstated — you can follow anyone from anywhere, so the interest match matters less than people suggest.

What actually matters: is it run by someone who seems likely to still be running it in two years, does it have a moderation policy you agree with, and is it big enough to be stable without being so big it is impersonal. If in doubt, join a general-purpose one. Moving later is a supported operation, not a disaster.

Once you are posting regularly, scheduling works differently here too — Mastodon has the feature, it is just not where you would look.