# Fediverse

The Fediverse (commonly shortened to fedi) is a collection of social networking services that can communicate with each other (formally known as federation) using a common protocol. Users of different websites can send and receive status updates, multimedia files and other data across the network. The term Fediverse is a portmanteau of federation and universe.
The majority of Fediverse platforms are based on free and open-source software, and create connections between servers using the ActivityPub protocol. Some software still supports older federation protocols as well, such as OStatus, the Diaspora protocol and Zot. Diaspora* is the only actively developed software project classified under the original definition of Fediverse that does not support ActivityPub.

## Design

While a traditional social networking service will host all its content on servers managed by the owner of the website, the decentralized structure of the Fediverse allows any individual or organization to host a social platform using their own servers (referred to as an "instance").
Every instance is independent, and can set its own rules and expectations. Even so, much like how users of one email service such as Gmail can still send emails to users of another service such as Outlook, users may still view content and interact with users on any other instance in the Fediverse. A user on one Mastodon instance, for example, may still view and interact with posts made by a user on a different Mastodon instance.
Instances hosted by different social networking services may communicate with one another as well. A user on the microblogging platform Misskey, for example, may view and interact with posts made by users on Mastodon. Some Fediverse networks even allow users to interact with different social networking formats from the same platform. For example, a user on a social news instance running Lemmy can interact with another post from an mbin instance, a similar service, as well as microblog statuses from Mastodon.

### Content moderation and user safety

Decentralized social networking platforms introduce new challenges and difficulties for user trust and safety. By nature of the Fediverse, operators of an instance are solely responsible for moderation of its content. As there is no form of centralized governance or moderation across the Fediverse, it is impossible for an instance to be "removed" from the Fediverse; it can only be defederated per an instance operator's choice, which makes that instance's content inaccessible from the operator's instance. Individual instances are responsible for defining their own content policies, which may then be enforced by its staff. Moderation of a Fediverse instance differs significantly from that of traditional social media platforms, as moderators are responsible not only for content posted by users of that instance ("local users"), but also for content posted by users of other instances ("remote users").
With toxic or abusive content being common in the Fediverse, as well as available moderation tools and the legal or financial impetus to moderate content lacking in comparison to those of centralized social media platforms, the Fediverse exhibits shortcomings in child safety. A 2023 study by the Stanford Internet Observatory's Cyber Policy Center found that, out of approximately 325,000 Fediverse posts analyzed over a two-day period, 112 were detected as instances of known child sexual abuse material (CSAM); 554 were detected as containing sexually explicit media alongside keywords associated with child sexual exploitation; 713 contained media alongside the top twenty CSAM-related hashtags on the Fediverse; and 1,217 contained text relating to distribution of CSAM or child grooming. The study additionally noted that, during a test run of its analysis pipeline, detection of its first instance of known CSAM occurred within approximately five minutes of runtime. All detected instances of CSAM were reported to the National Center for Missing and Exploited Children (NCMEC) for triage.
A 2024 paper observed that operators of Fediverse instances lack the ability to moderate content to the same standards as conventional social media, on both a logistical level and often also a technical level; however, they enjoy the same legal immunity under the United States' Section 230, "with none of the incentives to [moderate] anyway." The paper provides, as an example, instances whose purpose is specifically not moderating content, including "the second-largest Mastodon instance", which contains sexually explicit material of children.
Various solutions for development of content moderation and child safety on the Fediverse have been proposed. The Stanford Internet Observatory proposes development of distributable blocklists similar to BlueSky's functionality; mechanisms for pluggable hash matching and content classification (the same technology used by PhotoDNA); moderator tools such as grayscaling and blurring for certain report categories, as well as basic user fingerprinting; support and administrative interfaces for PhotoDNA and NCMEC CyberTipLine APIs; and a system of federated attestation of media analysis. Legal reform has also been proposed, most notably around Section 230 of the Communications Decency Act, as well as proposed legal requirements for instance operators to engage in good-faith moderation of instance connections.

## History
### Historical protocols

The concept and the functionality of the Fediverse has existed before the ActivityPub protocol and the term itself. One of the first projects that included support for a decentralized social networking service was Laconica, a microblogging platform which implemented the OpenMicroBlogging protocol for communicating between different installations of the software. The software was later renamed to StatusNet in 2009, before being merged into the GNU social project in 2013 along with Free Social, with the two latter servers being a fork of StatusNet.
Over time, the limitations of the OpenMicroBlogging protocol became more apparent, being designed as a one-way text messaging system. To replace the aging protocol, OStatus was devised as an open standard for microblogging, combining various other technologies like Salmon, Atom, WebSub and ActivityStreams into a single protocol used for communicating between instances. StatusNet first implemented the OStatus protocol on March 3, 2010, with version 0.9.0, and OStatus quickly became the most popular federated protocol in usage.
Around the same time as OStatus was gaining popularity, the diaspora* social network was formed, using its own federated protocol. To illustrate the differences between the two protocols, the terms of the Fediverse and the federation began to enter common usage, mainly after 2017. The term "the Fediverse" was used to describe the network formed by software using the OStatus protocol, such as GNU Social, Mastodon, and Friendica, in contrast to the competing diaspora* protocol under "the federation".

### ActivityPub

In December 2012, the flagship StatusNet instance at the time, identi.ca, transitioned away to a new software named pump.io, with a new federation protocol to replace OStatus. The new protocol was designed to be useful for general activity streams and not just status updates, and replaced many of OStatus' external dependencies with JSON-LD and a REST API for its messaging and inbox systems, as well as making more use of ActivityStreams. While not as utilized as its OStatus predecessor, it would end up becoming influential in the development of the ActivityPub standard.
In January 2018, the W3C presented the ActivityPub protocol as a recommended standard. The standard aimed to improve the interoperability between different software packages running on a wide network of servers and to succeed both the OStatus protocol and Pump.io. By 2019, almost all software that was using OStatus had added support for ActivityPub. While Mastodon began to remove OStatus support, other projects maintained it in their code, such as Friendica (which also maintained diaspora* support along with ActivityPub), and the term Fediverse has since come to mainly refer to the ActivityPub protocol and its supporting server software.

## Adoption

Users have been slow to embrace the Fediverse due to poor user experience and excessive complexity.
Following the acquisition of Twitter by Elon Musk in November 2022, certain major social networks, including Threads, Tumblr and Flipboard, expressed interest in supporting the ActivityPub protocol, as a large number of users began to migrate to Mastodon, a server that supported the Fediverse and was also the most popular alternative to Twitter at the time. Flickr also expressed support in supporting ActivityPub. As of November 2022, no information had been released by the company after the initial tweets by the CEO, with support for ActivityPub suspected to be on hold or cancelled.
In 2024, the local government of the Stary Sącz municipality in Poland launched their own PeerTube instance in order to de facto abolish its presence on YouTube. According to the government, they stopped using YouTube for official communications "in order to adhere to the appropriate regulations". In the same year, VIVERSE, HTC Vive's metaverse platform, implemented support for ActivityPub in their chat feature, allowing users to send direct messages to other fediverse users.

### Content management systems

WordPress has an officially supported plugin that integrates WordPress blogs into the Fediverse, allowing for comments to be exchanged between the comment section of a blog post and a Fediverse instance's reply function. The plugin was acquired by Automattic in March 2023, and became available for all WordPress.com users in October of that same year.
Ghost, a blogging platform and content management system, announced in April 2024 that they would be implementing Fediverse support via ActivityPub. The feature had been highly requested on its forums. In July 2024, Ghost started federating its development newsletter for the feature.

### Microblogging

Automattic CEO Matt Mullenweg tweeted on November 22, 2022, that Tumblr was adding support for ActivityPub interoperability, in response to a user's complaints about Mastodon's complexity. However, no further information was revealed for over a year, and was expected to be cancelled after a leaked reorganization that moved most of Tumblr's staff to other Automattic projects. However, following a question from a TechCrunch reporter during a questionnaire about the leaked memo, he revealed that the interoperability feature was not cancelled and that there was a small team working on studying the potential of implementing the protocol. The plan was once again affirmed by Automattic in January 2025, with the ActivityPub plugin for WordPress most likely being the main method used for interoperability with the fediverse.
The release of Threads by Meta in July 2023 had included in its press release that it planned to support interoperability with the ActivityPub protocol. In December 2023, select Meta employees began to federate with ActivityPub. A roadmap was revealed in January 2024 that detailed the integration of ActivityPub in Threads.
A faction of fediverse server admins, some of whom have listed their names under a pledge named "Fedipact", have expressed resistance to open federation with Threads over concerns that Meta would adopt an “embrace, extend, and extinguish" policy towards the network, or that Threads' moderation would fail to prevent the spread of abusive content targeted towards marginalized communities.
In March 2024, Threads implemented a beta version of Fediverse support, allowing Threads users to view the number of Fediverse users that liked their post, and allowing Fediverse users to view posts from Threads on their own instances. On April 2, the official Threads account for President Joe Biden enabled federation on its profile, making Biden the first President of the United States to have a presence on the Fediverse. The ability to view replies from the Fediverse within Threads was added in August.

### News aggregators

In December 2023, Flipboard announced that it started federating selected profiles and magazines with the Fediverse. It had previously run its own Mastodon instance, flipboard.social, as a test of the Fediverse.

## Alternatives

While the Fediverse has traditionally been the network most commonly referred to and used as an example regarding the subject of decentralized social networks, alternatives to it and the accompanying ActivityPub have been developed and deployed. A major protocol in competition with the Fediverse is the AT Protocol, which powers the Bluesky social network and has formed its own separate network dubbed by developers as the Atmosphere, while smaller competitors such as Nostr and Farcaster have become popular within the cryptocurrency community. These protocols have used ActivityPub in comparisons to their own architecture, as these newer protocols use a different federation model based on publishing content to relays for distribution rather than ActivityPub's server-centric model. Despite their differences, software exists that permit the bridging of user content between these protocols, including "double-bridges" that span multiple protocols for the purpose of distributing the same content.

## Software

ActivityPub is the most widely used protocol in the Fediverse and a W3C standard. Some popular Fediverse software includes:
* Content management system
** Drupal (via third-party plugin)
** WordPress (via official plugin)
* Image sharing/video sharing
** Pixelfed, an Instagram alternative
** PeerTube, a video streaming service similar to YouTube
* Macroblogging
** Friendica, an alternative to Facebook written in PHP
* Microblogging
** Mastodon, a microblogging social network written in Ruby
** Misskey, a popular Japanese social network written in TypeScript
** Pleroma, a lightweight microblogging server written in Elixir
* Social news
** Lemmy, a Reddit alternative written in Rust
** mbin, written in PHP