Line type
The classification of a phone number as mobile, landline, VOIP, or invalid.
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The classification of a phone number as mobile, landline, VOIP, or invalid.
Line type is the classification of a phone number by the kind of service behind it: mobile, landline, VOIP, or invalid. It is the single most useful attribute when deciding how to contact someone.
The distinction is operational, not academic. Mobile numbers can receive SMS. Landlines cannot — a text sent to one either fails silently or is converted to a clumsy automated voice call. VOIP numbers vary by provider, and some accept SMS while others do not.
Line type cannot be determined from the number format. Because of number portability, a number originally issued as a landline may now be mobile or VOIP. Establishing it requires a lookup against current carrier data.
Related terms
- Number portability — The ability to keep a phone number when switching from one carrier to another.
- Carrier lookup — Querying network data to find which carrier currently serves a phone number.
- SMS deliverability — The proportion of sent SMS messages that are actually delivered to a recipient handset.