NumberGlossaryLine Type
North America (concept is general) · also called line type lookup, wireline, wireless, landline vs mobile
The classification of a phone number by how its service is delivered — wireline (landline), wireless (mobile), or VoIP — not a fixed property of the number itself.
Line type classifies a telephone number by how the underlying service is delivered: wireline (a landline over metallic wire or optical fiber, terminating at a fixed location), wireless (a mobile service that uses electromagnetic waves rather than wire conductors), or VoIP (voice carried over an IP network). ATIS defines wireline as a network or terminal that uses metallic wire conductors and/or optical fibers, and wireless as one that uses electromagnetic waves rather than wire conductors. Line type describes the service technology, not the digits or format of the number — an ordinary 10-digit North American number can be delivered over any of these.
Line type is not a permanent attribute of a number. Under FCC local number portability rules, a number can be ported between wireline, IP, and wireless providers when the customer stays in the same geographic area, so the same digits can change delivery technology over time. Consequently, line type cannot be reliably inferred from the area code or prefix: because of thousands-block number pooling and portability, the old assumption that a prefix maps to one carrier and one service type no longer holds. Determining a number's current line type requires querying live routing data, not reading the number itself — and even then it reflects a present state, not a fixed classification.
A common belief is that you can tell landline from cell — or identify the carrier — from the area code or three-digit prefix. This was roughly true decades ago, but thousands-block number pooling and local number portability broke the prefix=carrier=type mapping. A number can be ported between wireline, VoIP, and wireless service, so its line type can change and cannot be read off the digits. The area code and prefix reflect a rate center and original assignment, not the current service technology.