pkreissel

We don't use application level IDs for this but global IDs. These are unique for users (at least we have no evidence otherwise).

Hi, this is actually incorrect. Facebook uses internal IDs (these are the ones used here, they are valid globally) AND external IDs for Apps and their connected pages. The external IDs have a completely different format and cannot be used to access a profile in the web browser (which is what we were able to do for all of them). We cannot completely rule out, that Facebook assigns two IDs to the same profile. However we think this is highly unlikely. We tried to check for that as far as possible. For example: If I search for a profiles name, that I found via a random ID lookup, and then check that profiles ID, its the same ID that was used in the lookup. We couldn't try this at scale though.