The fact of the matter is that there are now two standards – ATProto and ActivityPub – making the same fundamental claims to being the open standard that allows for decentralized social media.

Another fact is that ATProto and ActivityPub are architecturally very, very different. The former is what Christine Lemmer-Webber calls a “shared heap” structure, where an installation requires access to all the posts in the network, while the latter is server software that sends and fetches messages as the necessity arises. ATProto allows for “Personal Data Servers” – but these would rely on an infrastructure of indexes that likely will be prohibitively expensive. An ActivityPub server can run on a cheap server and still be a fully-fledged member of the fediverse.

Another fact is that both are overseen by very different bodies and both have come from very different processes. ActivityPub was developed at the W3C largely independent of corporate interests. The W3C remains the steward of ActivityPub. ATProto was born at Twitter and spun out into a separate, venture-capital funded corporation. While the Bluesky corporation promised in 2023 ATProto development will be shifted to the IETF, this still has not happened, and ATProto development is closely tied to a corporation that no doubt faces pressure to be profitable.