In AT Protocol, apps are consumers that sync data from users' hosting folders — the source of truth is always the user's own folder, not the app's database.
Dan describes how AT Protocol separates hosting from apps: each user's JSON records live in their own hosting folder, and apps sync from there. All events are streamed via websocket so apps update their databases, but the authoritative copy remains in the user's folder. ✦ AI generated
Dan Abramov · Syntax · 2026-07-29 · original ↗
starts at this moment · 14:22
when you write something on leaflet it actually creates a file in your folder on your hosting. ... if I follow you on blue sky, I'm actually creating a JSON like the app will create a JSON file in the blue sky follows subfolder of my folder on my hosting. So like every every action you do, you know, when I when you like you like my post, you're actually creating a JSON file in your folder under blue sky likes that has a link to a post in my blue sky posts folder in my repo. So it's kind of like a web of JSON with links. And so this is this is like what happens on the hosting layer is it's like the source of truth for like everybody's stuff that we created that is like available publicly you know with no permission. ... all apps listen to events from all hosts. ... all events are being streamed into all apps like through websocket and on your websocket listener in the app, it just puts it into your database. So you just filter out you know stuff that is the data that is relevant to your app.
verbatim transcript · starts at 14:22
14:22you know, you just use an app. Use the Blue Sky app or uh, you know, Tangled or like for G, you know, for Git repos or there's like a bunch of blogging like macro blogging apps like Leaflet, Offrint, uh, Pocket. So, these are all, you know, they work like normal sites. You just log into them, you have an account, you can like write something to publish. But these apps like the way
14:47they work is they're kind of like CMS's in a sense >> because when you write something on leaflet it actually creates a file in your folder on your hosting. >> Mhm. >> So it knows where your account's you know folder is and it just puts some JSON there. And it's the same like if I follow you on blue sky, I'm actually creating a JSON like the app will create
15:14a JSON file in the blue sky follows subfolder of my folder on my hosting. So like every every action you do, you know, when I when you like you like my post, you're actually creating a JSON file in your folder under blue sky likes >> that uh has a link to a post >> in my blue sky posts folder in my repo. So it's kind of like a web of JSON with
15:43links. And so this is this is like what happens on the hosting layer is it's like the source of truth for like everybody's stuff that we created that is like available publicly you know with no permission. It's just it's just like uh you can just you can just like grab it as as JSON and explore it. And then uh all apps listen to events from all hosts. So this is how you actually
16:07update your database, right? Because like apps, you know, you don't want to go to a thousand hostings to like calculate the number of likes. Like that would be stupid and and it wouldn't work, right? It's too slow. >> So what happens is that actually all events are being streamed into all apps like through websocket and on your websocket listener in the app, it just puts it into your database. So you just
16:30filter out you know stuff that is the data that is relevant to your app. You know like the blue sky server listens to blue sky events about blue sky records and like tangled server listens to events about tangled records. Uh, and some of them may actually like, you know, they may also care about something else, right? Like Tangled could decide to listen to blue sky follows and put
16:55the blue sky social graph into its own database and then show me what my, you know, friends are pushing to to Tangled. So, it's kind of like they they all can see each other's >> and it's at that app level where you would implement like an algorithm or um spam protection or or any of that stuff that that people would like cuz I think people coincide like