@cwebber ActivityPub is a federated social networking protocol for the World-Wide Web developed under the auspices of the World Wide Web Consortium (W3C). The 2018 specification document, a W3C Recommendation, was edited by Christine Lemmer-Webber and Jessica Tallon with contributions by Erin Shepherd, Amy Guy, and Evan Prodromou. Notable implementations of the protocol include Mastodon, Meta Threads, Pixelfed, and PeerTube.

The protocol's successor, OCapN, remains in development by Lemmer-Webber and Tallon's Spritely Networked Communities Institute and other contributors.