International HLR mobile validation

A live question to the network, not a guess from a database.

Every mobile network on earth keeps a Home Location Register (HLR), the central database that knows which SIMs are active, which network currently serves them, and whether that subscriber has been ported elsewhere. An HLR lookup asks that register a direct question over the SS7 signalling network and reads the answer back.

That matters because the alternatives are guesses. Prefix lists go stale the moment a number is ported. Regex tells you a number is shaped like a mobile, not that anybody answers it. Sending an SMS to find out costs money and tips off the recipient. An HLR lookup is silent, instant, and tells you the truth as the carrier sees it. The handset never rings and the subscriber never knows.

For UK and international marketing teams this is the difference between a dialler that connects and one that burns hours on dead numbers. It's also the cheapest place to catch a bad record: roughly a fifth of any aged contact list is disconnected, reassigned, or ported to a number that isn't routed there any more.