Carrier lookup

Lookup providers combine several data sources:

• Numbering-plan data: which operator the range was originally allocated to and what type of service the range is for.
• Number portability databases: where available, these record numbers that moved to another carrier, so the lookup can report the current one.
• Live network queries: an HLR lookup asks the mobile network's home location register about the number, which can also indicate whether it is active and reachable.

A typical response includes the country, current carrier name, network codes (MCC/MNC), line type, a ported flag and, for HLR-based queries, a reachability status. Numbers are normally submitted in E.164 format.

Before sending an SMS code, many platforms look up the number to decide how to treat it:

• Line-type filtering. Some services decline numbers reported as VoIP or landline and accept only mobile lines.
• Routing. Messaging providers use the current carrier to route texts efficiently.
• Fraud scoring. Recently ported numbers, unknown carriers or unreachable numbers can raise risk scores.

This is why two numbers that look similar can get different results: a number from a VoIP range may be refused at the first step, while a real mobile number passes the line-type check. Passing a lookup is only one signal, though; each service decides which numbers it accepts.

Lookup data is not perfect. Portability records can lag, some countries have no central database, and providers may classify the same number differently. A mismatch between what a number is and what a lookup reports is a common, and frustrating, reason for unexpected rejections. For a deeper look, read real mobile vs VoIP numbers and HLR lookups.