From IndieWeb

uid is a unique identifier.

IndieWeb examples

  • fluffy provides the uid microformat on the h-entry attributes using <data class="p-uid" value="ENTRY_UID"> from both h-feeds and individual entry pages; these UIDs match the matching GUIDs provided in the Atom feeds.

See Also

  • GUID
  • u-uid
  • Limitation: GUIDs on the web are not "G". While RSS & Atom assert that post GUIDs (and thus a h-entry uid) can be used to de-dupe entries (avoid new unreads) when a feed moves across domains, that assertion violates modern understanding and restrictions of cross-origin semantics, and cannot be expected to work. Assume such post GUIDs only work in the context of their domain.
  • Caution for 'uid' consuming applications: Even if you use a URL as your uid / GUID, you still need to be careful about how you treat it, like a malicious site alice.example.com could still provide a u-uid of https://bob.example.com/12345 and attempt to "overwrite" a post from another domain