# HLR lookup

> An HLR lookup queries a carrier's Home Location Register to learn whether a mobile number is active, which operator serves it and whether it has been ported, without sending a message.

The Home Location Register is the operator database of its subscribers. A lookup asks it about one number and returns its status (active, unknown, absent) and its current network, including after porting. Senders use it to clean lists before a campaign, so that dead numbers are removed without paying to send to them.

Lookups have limits: some operators answer inaccurately, some do not answer at all, and a number can go dead between the lookup and the send. A first small campaign with a good failure breakdown often cleans a list as well as a lookup.

At SMSMeteor: the delivery report flags unknown numbers after the first send so they can be removed in one click; rejected and unknown-prefix rows never cost anything.

Related terms: [Unknown subscriber](https://smsmeteor.com/glossary/unknown-subscriber), [Mobile number portability (MNP)](https://smsmeteor.com/glossary/number-portability), [Delivery rate](https://smsmeteor.com/glossary/delivery-rate)

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Source: https://smsmeteor.com/glossary/hlr-lookup (HTML). Generated by SMSMeteor from the same data as the page. Summary of the whole site: https://smsmeteor.com/llms.txt