The fediverse is a network of independently run servers and apps that talk to each other over open protocols, chiefly ActivityPub. One account on any server can follow and interact with accounts on other servers, much as email works across providers.
What the fediverse is and how it differs from centralized platforms
The name is a blend of “federation” and “universe”. Mastodon’s documentation describes it this way: “The fediverse (“federated universe”) is the name for all websites that can communicate with each other over ActivityPub and the World Wide Web.” The definition is deliberately broad. It names no single company, app or domain, only a shared way of communicating.
Traditional social media works differently. A conventional service hosts all of its content on servers managed by the owner of the website. The fediverse’s decentralized structure, by contrast, allows any individual or organization to host a social platform and still connect to everyone else. The result is closer to a family of cooperating sites than a single destination. A federated social network is the general term for this arrangement, and the fediverse is its largest real-world example.
Centralized, federated and distributed
Mastodon’s documentation places networks on a scale of centralization. It states that federation is a form of decentralization, and it sorts examples into three groups: centralized (Twitter, Facebook, Instagram), federated (email, XMPP, phone networks, physical mail) and distributed (BitTorrent, IPFS, Scuttlebutt). Federated systems sit in the middle. Each server is run by someone, and users depend on that operator, but no single operator controls the whole network.
The email comparison is the most useful one for newcomers. The documentation says that, just like you can send an email from your Gmail account to someone from Outlook, Fastmail, Protonmail, or any other email provider, a user can mention or message anyone on any compatible website using their address. A Mastodon address therefore looks like an email address with an extra at-sign in front.
What a user actually experiences
A new user picks a server, creates an account and then follows people on that server and others. Mastodon’s own site promises that users can follow anyone across any Mastodon server from a single account and receive posts in chronological order. Moving between servers is possible, and the documentation has a section on moving or leaving accounts. The choice of server matters mainly for culture, moderation rules and who administers the hardware, not for who a user can reach.
How federation works: ActivityPub, WebFinger and actors
Three technical pieces do most of the work: a protocol for delivering activities, a data format to describe them, and a lookup method to find people on other servers.
ActivityPub
ActivityPub is the shared language. According to Wikipedia’s summary of the standard, it provides a client-to-server (C2S) API for creating and modifying content, as well as a federated server-to-server (S2S) protocol for delivering notifications and content to other servers. In practice, most of the visible fediverse relies on the server-to-server half. Apps and websites then expose their own user interfaces on top of that.
The content itself is structured data. The same article notes that ActivityPub uses the ActivityStreams 2.0 format for building its content, which itself uses JSON-LD. Every user is an “actor”. Every actor type contains an inbox and outbox stream, which sends and receives activities for a user. To publish something, an actor places an activity in its outbox, and the server delivers it to the inboxes of the recipients.
Mastodon’s technical documentation lists the activities involved in following. A follow request indicates interest in receiving status updates from a profile. Mastodon says that unlocked accounts will automatically reply with an Accept, while locked accounts can manually choose whether to approve or deny a follow request.
WebFinger and the @username@domain address
An address alone is not enough to deliver a message. Mastodon’s WebFinger page explains that a Mastodon user’s full mention consists of both the username and the domain, in the form @username@domain. To deliver over ActivityPub, that mention must first be translated into an HTTPS address so the remote actor’s inbox and outbox can be found. The page adds that WebFinger as described in RFC 7033 is a spec that defines a method for resolving links to a resource, given only a URI on a particular server. WebFinger is therefore the phone book of the fediverse.
A short history from OStatus to ActivityPub
The fediverse did not appear fully formed. Its roots lie in earlier federated microblogging, and the older protocols explain why the ecosystem still contains some legacy features.
StatusNet, GNU social and OStatus
Wikipedia reports that the software that became StatusNet was renamed to StatusNet in 2009, before being merged into the GNU social project in 2013. Its first federation protocol, OpenMicroBlogging, was designed as a one-way text messaging system, and its limits became apparent. The replacement was OStatus, and StatusNet first implemented the OStatus protocol on March 3, 2010, with version 0.9.0.
OStatus had a drawback. Per the ActivityPub article, it was built using a multitude of technologies (such as Atom, Salmon, WebSub and WebFinger), which made it difficult to implement in new software. Originally the word “fediverse” referred only to the network formed by OStatus software such as GNU Social, Mastodon and Friendica. A competing system, the Diaspora network, used its own protocol.
The W3C standard
The turning point was standardization. Wikipedia records that the standard was first published by the World Wide Web Consortium (W3C) as a W3C Recommendation in January 2018 by the Social Web Working Group. Development later moved to the Social Web Community Group. The standard aimed to improve interoperability between different software packages, and the Fediverse article says that by 2019, almost all software that was using OStatus had added support for ActivityPub.
One notable holdout remains. The same article says that Diaspora is the only actively developed software project classified under the original definition of Fediverse that does not support ActivityPub. Some software also keeps support for older protocols such as OStatus, the Diaspora protocol and Zot, so bridges between the old and new worlds persist.
The main platforms and what each does
Because the fediverse is a protocol rather than a product, many different apps share it. Each one specializes in a type of content. Wikipedia notes that a user on Misskey, for example, may view and interact with posts made by users on Mastodon, and that a Lemmy user can interact with posts from mbin, a similar service, as well as microblog statuses from Mastodon.
Microblogging: Mastodon, Pleroma and Misskey
Mastodon is the best-known platform. Wikipedia says it was first released in 2016 by Eugen Rochko. On a standard instance, posts can include up to 500 text-based characters, greater than Twitter’s 280-character limit. Mastodon’s own site states that Mastodon is free and open-source software, and Wikipedia identifies the license as AGPLv3.
Mastodon has kept shipping features. According to Wikipedia, Mastodon 4.0 was released in November 2022, including language support for translating posts, editing posts and following hashtags, and Mastodon 4.5 followed in November 2025, introducing quote posts among other features.
Pleroma offers a lighter server aimed at small hosts, and Misskey is a feature-rich microblogging platform with a strong following in Japan. Both interoperate with Mastodon. The WordPress ActivityPub plugin lists its tested federated platforms as Mastodon, Pleroma / Akkoma, friendica, Hubzilla, Pixelfed, Socialhome and Misskey, which gives a quick picture of the main family of compatible software.
Link aggregation, photos and video
Not every fediverse app resembles a microblog. Lemmy works as a link aggregator and discussion forum, in the style of a social news site. Pixelfed is built around photo sharing, and PeerTube hosts video. Wikipedia’s software table also lists tools for audio hosting (Funkwhale), event management (Mobilizon), forums (NodeBB) and live video streaming (Owncast), all of which speak ActivityPub.
The common thread is that an account on one of these apps can often be followed from another. A video published on a PeerTube server can appear to a Mastodon user as a post, and a reply can come back to the video page. The experience is not always seamless, because each app only displays the fields it understands. Mastodon’s documentation, for instance, lists the HTML it accepts from remote posts and sanitizes the rest, so formatting can differ between platforms.
Growth moments and adoption
Adoption has come in waves, usually triggered by dissatisfaction with large platforms. Wikipedia reports that Mastodon’s global use had risen from 766,500 users as of 1 August 2017, to 1 million users on 1 December 2017. Another spike came in 2018 over privacy concerns. The largest surge followed Twitter’s acquisition by Elon Musk in 2022. During that period, the number of new users of the platform compared to the previous week was reported to be 700,000 on 11 November, moving Mastodon past 7 million users.
Large companies have since moved closer to the network. Wikipedia describes Meta’s Threads as interoperable with Mastodon through ActivityPub, a connection that brought the fediverse to many people who had never heard of it. Mastodon’s article says Mastodon is interoperable with other ActivityPub-based platforms, such as Threads. Not all derivative projects are welcome, though. Truth Social, founded in October 2021, was built on Mastodon, and Wikipedia notes that it initially did not make its source code available, violating Mastodon’s AGPLv3 license.
Choosing between joining and hosting
Anyone interested in the fediverse can join an existing server, which takes minutes, or run one. Hosting means taking on updates, backups and moderation duties. Readers who want to understand the trade-offs can consult the guide to the self-hosted community, which covers what running your own infrastructure involves. Another guide covers the wider open source social network landscape, including options that are not federated at all.
Practical advice for newcomers
A few habits make the first weeks easier. Browsing the public server directory on Mastodon’s site helps compare servers by topic, language and moderation approach. Following a handful of accounts from different servers shows how the home timeline mixes them. Searching for a full address, with the username and domain, is the most reliable way to find a specific person on another server.
Newcomers should also expect differences between apps. A photo-first app may hide long text, a forum app may present replies as threaded discussions, and a microblog may flatten them into a timeline. None of this breaks federation. It reflects the fact that each project decides how to display the same underlying activities, and that variety is part of why the network has stayed lively and experimental.
Moderation, defederation and trust
Decentralization changes how abuse is handled. Wikipedia observes that decentralized platforms introduce new challenges for trust and safety, and the Fediverse’s structure means there is no central referee.
Each server sets its own rules
The Fediverse article puts it directly: as there is no form of centralized governance or moderation, it is impossible for an instance to be “removed” from the Fediverse; an offending instance can only be defederated by other instance operators’ choice to make its content inaccessible from their instances. Individual instances define their own content policies, and their staff enforce them. A user who dislikes a server’s rules can move to another.
Wikipedia adds that Mastodon’s founder believes that small, closely related communities deal with unwanted behavior more effectively than a large company’s small safety team. Critics counter that volunteer moderators can be overwhelmed, and that the quality of moderation varies from server to server.
The moderation toolkit
Mastodon’s administrator documentation describes several levels of action against individual users and entire sites. The user-level options are sensitive, freeze, limit and suspend, and the server-level options include reject media, limit, suspend and a blocklist. Of the limit setting, the documentation says it was previously known as “silencing”, and that a limited account is hidden from all other users on that instance, except for its followers. It also covers spam-fighting measures such as blocking by e-mail server and by IP.
Practically, a new user should read a server’s rules and its blocklist policy before signing up. Different servers take different approaches, from open registration with active moderation to invitation-only communities. A broader look at the tools used to build and run these spaces sits in the guide to the community platform ecosystem.
Beyond social apps: blogs, publishing and rival protocols
The fediverse is spreading beyond dedicated social apps and into publishing tools. Wikipedia says the WordPress plugin was acquired by Automattic in March 2023, and became available for all WordPress.com users in October of that same year. It also reports that Ghost, a blogging platform, announced in April 2024 that it would implement fediverse support via ActivityPub.
The plugin’s own page explains the appeal for site owners: it lets a site attract followers, deliver updates, and receive comments from a diverse user base of ActivityPub-compliant platforms. A person can follow a blog from a Mastodon account, and replies appear as comments. The plugin notes that once it is installed, only new posts going forward will be available in the fediverse.
Competing models: Nostr, Farcaster and others
ActivityPub is not the only approach to decentralized social media. Wikipedia notes that smaller competitors such as Nostr and Farcaster have become popular within the cryptocurrency community. These newer protocols use a different federation model based on publishing content to relays, rather than ActivityPub’s server-centric model. Bluesky is also described by Wikipedia as part of the broader shift toward decentralized social networks.
For readers, the practical meaning is that “decentralized” covers several architectures that do not interoperate by default. The fediverse proper is the group of sites that speak ActivityPub. Other networks can connect through bridges, but those are separate projects with their own limits.
Frequently asked questions
Is the fediverse one website?
No. It is a set of independently run servers that exchange posts over ActivityPub. Mastodon’s documentation defines it as all websites that can communicate with each other over ActivityPub and the World Wide Web.
Do I need a Mastodon account to use it?
No. Mastodon is one of many compatible apps, including tools for photos, video and forums. Accounts on those apps can usually be followed from Mastodon and from each other, though features differ by software.
Who controls the fediverse?
No single party does. Each server operator sets local rules, and other operators can choose to defederate from servers they consider harmful. Wikipedia notes that an instance cannot be removed from the network centrally.
Is ActivityPub an official standard?
Yes. The W3C published it as a Recommendation in January 2018, according to Wikipedia. Development continued afterward in the Social Web Community Group.
Can I run my own server?
Yes. Mastodon is free and open-source software, and its documentation includes a section on running your own server. Operators take on updates, backups and moderation, so many people join an existing server instead.
