What is an HLR lookup?
An HLR lookup is a query of the Home Location Register, a group of databases which operators continuously update in order to provide information on mobile numbers. Information provided on the HLR includes the validity of the phone number, network details, porting information and details on whether or not the phone number is roaming.
Please note: Accurate HLR data cannot be retrieved for mobile numbers in Brazil, Canada and the USA so number validation is not possible. Regularly updated Mobile Number Portability (MNP) databases can be queried instead of performing HLR lookups for these 3 countries purely for the purposes of network identification.