Glossary · Phone
Mobile number portability
The right to keep a phone number when switching carriers, which breaks the link between a number's prefix and its current network.
Portability means the carrier that was originally allocated a number block is often not the carrier serving the number today. Any lookup based purely on prefix data reports the original assignment.
Resolving the current carrier requires either portability database access, which is regulated and normally limited to telecom entities, or a live query against the network.
A tool that reports an assigned carrier without saying which kind of answer it is giving is misleading. Ours labels it as the assigned block rather than implying a live result.