Authentication between instances is not federated.
Posted content is “sync’d” between instances.
Apps log into the instance using your creds on that instance to access the content that’s syncs to that instance.
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Authentication between instances is not federated.
Posted content is “sync’d” between instances.
Apps log into the instance using your creds on that instance to access the content that’s syncs to that instance.
They are different platforms, so you can't. If you remove ActivityPub from one Lemmy instance (or server), it would be just one centralized Reddit clone. What makes them special is that every public activity (like, comment, post, etc.) are all sent to other servers in the whitelist. This causes the other instances to also have the same content (copy), making the fediverse possible. Just because you can comment on your instance and that being displayed on some Mastodon instance does not mean you have another account there. Your comment was simply copied to that other Mastodon instance using the ActivityPub protocol.
If you want this so you can claim your comments, posts, likes, etc. on other federated platforms (e.g. Lemmy -> Mastodon), you can look into DIDs. DIDs allow users to have Decentralized IDentifiers. Which means the identity that your content are linked to is not locked into one instance. You can log in with your DID(s) anywhere that supports them.
The thing is that DIDs are still being discussed (or had been discussed) to decide how it would be implemented into ActivityPub. Bluesky, for example, uses DIDs. Which is why you can claim the ownership of your content from one instance on another. Do note that Bluesky does not use ActivityPub, but their own protocol called the AT protocol (which, in my opinion, just exists because they want to be different).
@nostupidquestions Hmm. Just logged in through another app and it said server is using unsupported software
@Reshirams_Rad_Slam @nostupidquestions this would be possible if someone made a platform that implemented the same APIs for both mastodon and lemmy, but would fail if there was a platform they didn't implement say Loops and you tried to log into their app. A few fedi microblogging platforms like Plemora already implement Mastodon's api to allow using the Masto apps with their instances for free.
Federated identity is something being worked on, but will be likely be seperate to AP itself.
I tried that when I first got here last year. I'll spill the beans, you simply can't do it. Despite both Mastodon and Lemmy supporting the ActivityPub protocol, they are different platforms. You can exchange posts and comments and whatnot, but you can't use an account from one platform to log into another.
Just like email, you can't log into Proton Mail with a Gmail account, and vice versa, despite both platforms being able to exchange emails (because duh, that's how email works).
I hope that explains everything.