Mastodon and the W3C: The Pub is Now Open, ActivityPub that is! - Official Mastodon Blog | Sept 2017

"Mastodon is a free, open-source federated social network spanning over 800,000 users spread across more than 2,000 servers. Mastodon v1.6 is here, and it is the first Mastodon release which fully implements the ActivityPub protocol. ActivityPub is a new federated messaging protocol developed by the World Wide Web Consortium (W3C) which aims to fix the shortcomings of past standards like OStatus. Mastodon is one of the first platforms, and certainly the first major platform to implement this new standard and prove it in the wild. It was a natural upgrade for our project, as we long ago reached the limits of what OStatus was capable of. And what we needed was better privacy, better defaults, better cryptographic verifiability, and better distribution mechanisms. This protocol is also very flexible in what it allows you to express and it is naturally extensible as it is based on JSON-LD. Besides allowing Mastodon to fully and reliably exchange the data it currently needs to exchange, it also has a lot of potential for future developments in the area of distributed identities and end-to-end encryption...."