Upgrading design to serve people
Bluesky
X (formerly Twitter)
AT Protocol (atproto) is a new foundation for building decentralized social apps — meaning apps like Twitter or Reddit, but where users control their data and identity instead of a single company.
It’s part of the Bluesky project, and its goal is to keep the freedom of the early internet while also keeping the smooth, modern experience people expect from today’s social media.
Atproto combines ideas from three big movements in tech history:
Old web (Web 1.0): Anyone could publish a page if they had a computer and internet connection. No central gatekeepers.
Modern web (Web 2.0): Easier to use, but now controlled by giant platforms (Facebook, YouTube, etc.).
Takeaway: The web taught openness and hyperlinking — but we lost independence when everything got centralized.
P2P systems (like BitTorrent) remove central servers — users’ devices share data directly.
Data is self-certifying, meaning it carries its own proof of authenticity (cryptographic signatures).
Problem: P2P is hard to keep consistent, data can vanish if peers go offline, and it’s too heavy for user devices.
Takeaway: Great for independence, but bad for speed, reliability, and user experience.
Big web platforms learned to handle massive amounts of data using distributed databases, event logs (like Kafka), and microservices.
Takeaway: These systems are powerful, fast, and reliable — but tightly controlled by corporations.
Atproto takes the best parts of all three:
| From… | It Keeps… |
|---|---|
| Web | Openness, permissionless access, universal connectivity |
| P2P | User-controlled data, cryptographic trust, no central authority |
| Distributed Systems | Scalable performance, low latency, reliability |
Instead of organizing data by location (like websites) or file hashes (like P2P), atproto organizes data by user identity.
Example: an atproto link looks like at://username/post/123
Your data belongs to you, not to the server that hosts it.
Your posts live in a Personal Data Server (PDS) — which you can move to another host anytime without losing your identity.
So, your handle and content stay portable — like taking your followers with you if you leave Twitter.
The protocol keeps data hosting simple and universal — just store and verify user data.
Meanwhile, apps built on top (like social networks or search tools) can innovate freely, using that open data.
This avoids “vendor lock-in.” You can switch apps or hosts without losing your data or network.
→ Compare this to Mastodon:
Mastodon uses servers (“instances”) that are tightly coupled with your account and data. If your instance shuts down, you may lose your content or connections. Atproto solves this by separating identity and data hosting from apps, making migration easy and reliable.
Atproto is intentionally structured — strict data formats and schemas — to prevent chaos and make apps interoperable.
Instead of everyone “sort of speaking the same language,” atproto forces systems to definitely speak the same one.
This makes it easier to build reliable, compatible tools without endless patching.
Traditional web: you must fully trust a platform (like Facebook).
Pure P2P: you trust no one but your device — too slow and complex.
Atproto: middle ground.
Trust is built into the data itself (cryptographic verification).
Apps can show you “computed views” (like timelines) without re-verifying everything — as long as users can prove if something’s fake and move elsewhere.
Users can always migrate away if a server or app behaves badly — a principle called “credible exit.”
| Challenge | Mastodon / ActivityPub | Atproto |
|---|---|---|
| Account Portability | Moving servers is hard; you can lose data or followers | Identity moves easily between hosts (PDS) |
| Data Ownership | Instance owns your posts | You own your posts, hosted anywhere |
| Performance | Federated servers can be slow or inconsistent | Uses proven cloud-style systems for speed |
| App Innovation | Tightly tied to servers | Apps can innovate freely on open data |
| Trust Model | Must trust each server fully | “Lazy trust” – data is verifiable, but UX remains smooth |
| Scalability | Small-scale federation | Designed for billions of users |
Atproto aims to deliver the freedom of decentralization without the fragility of old P2P networks or the lock-in of corporate platforms.
It treats your identity as the center of the internet, not the app or server.
That means you own your digital self, your data, and your connections — while still getting the fast, smooth experience of modern social apps.
Get in touch with Prof Joline Blais or TA Cecilia Andrade via