The fediverse is an ensemble of social networks which can communicate with each other through a common networking protocol (ActivityPub) while remaining independent platforms. Users on different social networks and websites can send and receive updates from others across the network.
The term fediverse was first used to describe the network formed by software using the OStatus protocol, such as GNU Social, Mastodon, and Friendica.
In January 2018, the W3C presented the ActivityPub protocol, aiming to improve the interoperability between different software packages run on a wide network of servers. By 2019, a majority of software that was previously using OStatus had switched to ActivityPub, and the term "fediverse" came to refer to the ActivityPub-based federated network.