The Social Web Working Group has published a Proposed Recommendation of ActivityPub. The ActivityPub protocol is a decentralized social networking protocol based upon the [ActivityStreams] 2.0 data format. It provides a client to server API for creating, updating and deleting content, as well as a federated server to server API for delivering notifications and content.
ActivityPub is already implemented and deployed to a number of projects and a wide userbase, including over 1 million registered users across thousands of Mastodon instances. It provides the possibility to build social network capabilities into small or large scale software projects which may or may not present social network as their core offering.
Comments are welcome through 2 January 2018.