Line Type Lookup: Mobile, Landline and VoIP
Line type lookup explained: what mobile, landline and VoIP labels mean, how teams use them in CRM and review workflows, and what they do not show.
Defines the line types a lookup can report and shows practical ways data teams use them, with clear limits on what a line type result means.
A line type lookup labels a phone number by the kind of line it belongs to, such as mobile, landline or VoIP. CarrierLookup returns a number type alongside the originally allocated carrier, the underlying carrier, the country code, and region and city allocation geography. Teams use the label to organise lists and route records to the right review path. It describes how a number was allocated, not whether the number is active or who holds it.
What a line type lookup tells you
A line type is a category attached to a number range. The common categories are:
- Mobile: numbers allocated for mobile service.
- Landline: numbers allocated for fixed lines.
- VoIP: numbers allocated for internet-based voice services.
Other vendors, such as Twilio's line type intelligence, publish their own category lists, and the exact labels differ between providers. Read the documentation of the service you use rather than assuming a shared vocabulary.
CarrierLookup reports the value as a number type. It can be empty, and an empty value means the label is unavailable for that number, not that the number is invalid.
How teams use line type in practice
The label is most useful when it feeds a decision that a person or a rule still reviews:
- Segment a CRM export. Split contacts into mobile, landline and VoIP groups before choosing which channel plans apply to each.
- Prioritise review. Send records with unexpected types, for example a VoIP number on a form that expects a personal mobile, to a manual queue.
- Audit list sources. Compare the type mix of two lead sources to see which one carries more fixed-line numbers.
- Prepare enrichment. Add type and carrier columns so later steps can filter without another lookup.
The label supports these steps, but it should be one input among several, not a final verdict.
Running the lookup
For a handful of numbers, a realtime check returns the number type in the same response. POST /api/v1/check takes one E.164 number, and POST /api/v1/batch-check takes 1 to 100 numbers and returns them in input order. The dashboard accepts up to 500 numbers for a realtime multi lookup.
For a large single-country list, a bulk file task accepts a TXT or CSV file and returns one CSV with the number type for each completed row. Bulk identifiers are plain digits with the country code and no plus sign, so match them back to the source list on that basis.
Both paths draw on the same balance, and failed or undetermined lookups do not keep a charge.
What a line type does not prove
A line type is not a reachability check. A mobile label does not show that a number can receive a call or text, and a landline label does not show that it cannot be used in some other way. The result also says nothing about who owns the number or whether they agreed to be contacted.
Because the type comes from number-range allocation, a number that moved to another service after allocation may still carry its original label. Teams should record the lookup date, keep the raw number, and treat the label as context. Writing that expectation into the review guide helps new analysts read the column correctly.
FAQ
Does a mobile line type mean a number can receive messages?
No. The line type describes how the number range was categorised. It does not test reachability, activity or consent. Teams that need to send messages should rely on their own sending checks and permissions, and use the line type only to organise their records.
What does an empty number type mean?
It means the value is unavailable for that number. A completed lookup can return empty carrier and type values and still be a completed result.
How can teams use VoIP labels without over-reading them?
Treat a VoIP label as a reason to look closer, not as a conclusion. A reviewer can combine it with form context and other signals, then decide what to do. The label alone says nothing about identity, intent or ownership.
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