Sarah's Tech · Episode 18 · Show notes

Anatomy of the AT Protocol

The picture behind the episode. Four parts move a post through this network — and W Social operates one of them. The names in brackets are the ones we used on air.

HOW A POST TRAVELS your finished timeline App Bluesky, W Social, third-party clients Your logbook Personal Data Server signed records The wire Relay bsky.network The newsroom AppView timeline, search, counts writes commit events firehose HOW IDENTITY RESOLVES Handle ec.europa.eu Permanent ID did:plc:oxo226vi7t2… The register plc.directory Server address pds.wsocial.network resolves to looked up in returns points at the logbook
Every post takes two routes. Above, the data: you only ever write into your own logbook, and you read from the newsroom, which indexes the wire. Below, identity: the handle is just a pointer, the permanent identifier never changes, and the register is the book that connects the two to a server address.

What the register actually is

A permanent identifier such as did:plc:oxo226vi7t2btjokm2buusoy is a durable, meaningless string. On its own it does not say where your data lives or which keys sign your posts. That is what the PLC directory holds: for every identifier, a small versioned entry with the public keys, the current handle, and the address of the server that keeps the logbook.

The abbreviation originally stood for placeholder — a stopgap until something better existed. The stopgap is still running, operated by Bluesky Social PBC. Handing it to a Swiss association has been announced. It has not happened.

This is why there is no contradiction in the European Commission posting as ec.europa.eu while its data sits on pds.wsocial.network. The handle can be changed. The storage location can be moved. Only the permanent identifier is fixed — and its entry lives in a directory under American control.

You can check this yourself. Resolve the handle to its identifier, then fetch that identifier's document from plc.directory and read the service endpoint. It takes two requests and no account.

WHO OPERATES WHAT Bluesky Social PBC, USA W Social W Social AB, Sweden Eurosky Stichting Modal, NL The logbook — your data The wire — distribution The newsroom — visibility The register — identity operates it planned uses someone else's
The logbook is the cheap part, which is why everyone has one. The wire and the newsroom are the expensive parts, and nobody outside the United States runs either. Identity is the layer nobody has touched at all.

The terms

PDSthe logbook
The server holding your repository: posts, likes, follows, each one a cryptographically signed record. Anyone can run one, including a hosting company on behalf of its customers. Moving is designed in — the repository travels with you, the permanent identifier stays.
Handleyour name
A domain name used as a human-readable pointer to the permanent identifier, proven with a DNS record or a file on the web server. Interchangeable — which is why an institution can display its origin while the technology behind it sits somewhere else entirely.
DIDpermanent identifier
The durable identity of an account, independent of name and server. Almost always did:plc:… here. The alternative, did:web, hangs off a domain you control and needs no central directory — and is barely used.
PLC directorythe register
The directory mapping every did:plc to its keys, its current handle and its server address. Operated by Bluesky Social PBC. The single most concentrated point in the system: whoever controls it controls where every account can be found.
Relaythe wire
Collects changes from every logbook into one stream of events, the firehose. Anyone may run one — but doing so means receiving the entire network, which is where decentralisation meets the hosting invoice.
AppViewthe newsroom
Reads the firehose and builds what you actually see: timelines, reply threads, counts, search. Whoever runs it decides visibility, which makes it the moderation layer as well.
PBCa company form
Not part of the protocol. A US legal form — a corporation permitted to pursue a stated public benefit alongside profit. Bluesky Social PBC is the venture-funded company behind the app, the relay, the AppView and the register.