ActivityPub is an open, decentralized social networking protocol based on's ActivityPump protocol.[1] It provides a client/server API for creating, updating and deleting content, as well as a federated server-to-server API for delivering notifications and content... The social networking software, Mastodon, implemented ActivityPub in version 1.6, released on 10 September 2017. It is intended that ActivityPub will offer more security for private messages than the current OStatus protocol does.

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