OpenWebAuth -
https://zotlabs.org/page/zot/specs+openwebauth - is on the way to Pixelfed
https://github.com/pixelfed/pixelfed/pull/4339and more to come
OpenWebAuth provides a light-weight form of cross-domain authentication between websites on the open web.
This PR shows how Pixelfed users could log in as visitors on OpenWebAuth enabled services like Hubzilla and the project nicknamed "Streams" or any Fediverse server which implements the server-side of OpenWebAuth. Pixelfed users do not need an account on the other server.
In practice, it depends on the services and the permissions that the Pixelfed user has on the other server's services; e.g. a user on Hubzilla or Streams could allow a Pixelfed user to post on his wall, upload a picture to his cloud etc.
Note: this is only the 'client' side of the protocol i.e. Hubzilla/Streams users could not log in to Pixelfed.
to see how OpenWebAuth works have a look here:
https://videos.im.allmendenetz.de/w/pGfRdAVVsDMH4QFVGearkw