AT Protocol is fundamentally different from Mastodon/ActivityPub: Mastodon is like federated app instances that email each other, while AT Protocol is a shared data layer where apps consume from a common open web of JSON.
Dan contrasts Mastodon (federated Twitter instances that sync via ActivityPub 'mailing' messages between servers) with AT Protocol (a single open data layer where apps independently consume everyone's JSON). He argues Mastodon ties identity to an instance, while AT Protocol separates identity, hosting, and apps. ✦ AI generated
Dan Abramov · Syntax · 2026-07-29 · original ↗
starts at this moment · 37:02
“How is this different than like mastedon where like I'm I'm not even sure I totally understand how mastedon works.”
the way I like to think about Masttodon is Masttodon is kind of like it's kind of like WordPress. So, it's it's kind of like, you know, it's an it's like a mini Twitter that you can install on your server and that server is does the entire thing, right? Like it's it's like a like a hosted Twitter. So you just you just spun out a copy of the app and so you can imagine there's like you know like if you if there is a copy running at like instance one.com you sign up there your account is there like that is that is the Twitter you signed up for right and then like if there's another instance is completely independent hosting completely independent app ... And then the problem is like okay first problem is like your your identity is actually inside that app right like if if somebody removes that server from the internet like your you know your like your identity was there. ... these instances have to talk to each other right because if I follow you but you're in another instance what happens is these like copies of Twitter start sending like emails to each other in a sense, right? Like they like activity pub is kind of like like a mailbox uh abstraction where you like these instances start messaging each other and saying actually like Wes has posted ... So you have this like n squared divided by two connections between instances where they like send stuff to each other ... it's many apps that are disconnected that try to sync to each other via email is like my my kind of mental model.
verbatim transcript · starts at 37:02
36:44not honor this delion just like today somebody who's not nice can like screenshot your Twitter pages like whenever you post or whatever. >> Um how is this different than like mastedon where like I'm I'm not even sure I totally understand how mastedon works. you know, I have my threads that are posted out to Mastadon instances, but some people reply and I'm not able to reply to them cuz I don't know where
37:08they are. Um, but like this this is not the same thing as Mastadon, right? >> Yeah, it's pretty different. So, the way to think the way I like to think about Masttodon is Masttodon is kind of like it's kind of like WordPress. So, it's it's kind of like, you know, it's an it's like a mini Twitter that you can install on your server >> and that server is does the entire
37:33thing, right? Like it's it's like a like a hosted Twitter. So you just you just spun out a copy of the app and so you can imagine there's like you know like if you if there is a copy running at like instance one.com you sign up there your account is there like that is that is the >> Twitter you signed up for right and then like if there's another instance is
37:58completely independent >> hosting completely independent app and like if if your friend makes an account there is it's like a different service like they have nothing to do with each other. It's just somebody else's app who is like administered by whoever is running it. And then the problem is like okay first problem is like your your identity is actually inside that app right like if if somebody removes that
38:22server from the internet like your you know your like your identity was there. So it's it's kind of um like it's not really like a network. I think of it as similar as to um kind of like kingdoms in like ancient China or like you know like fdoms where like you belong to this clan or whatever like there is you know there's like part of the map that is that is like your
38:52instance and then maybe if your friend lives somewhere else like these instances have to talk to each other right because if I follow you but you're in another instance what happens is this these like copies of Twitter start sending like emails to each other in a sense, right? Like they like activity pub is kind of like like a mailbox uh abstraction where you like these instances start messaging each
39:17other and saying actually like Wes has posted and like this instance was interested in you know in somebody here follows him so I'm going to send like really all west posts here. So you have this like n squared divided by two connections between instances where they like send stuff to each other that >> uh you may have missed but it's very fragmented because like even if you try
39:41to like patch it with like loading stuff from other instances or like you know assembling like on it's kind of you know it's it's many apps that are disconnected that try to sync to each other via email is like my my kind of mental model. Uh, and every and you're tied to a specific one. And like for example, if admins of one instance decide to have beef with admins of