https://pagedigest.org/rel
This URL is a Web Linking (RFC 8288) extension relation type. A link with this relation identifies a pagedigest manifest for the origin: a JSON document of per-URL monotonic revisions that lets automated clients detect content changes with one request.
Publishers advertise the manifest on ordinary responses:
Link: </.well-known/pagedigest.json>; rel="https://pagedigest.org/rel"
Clients should treat this URL as an identifier for the relation's semantics, not as a resource to dereference during ordinary operation. This page exists for the humans who dereference it anyway.