Carrier and Line-Type Lookups: A Practical Guide

Before you can act on a phone number, you have to understand it. Carrier and line-type lookups turn a raw string of digits into structured intelligence: who operates the number, what kind of line it is, and whether it carries the traits that correlate with risk. This guide breaks down the key fields and how to read them.

The core fields

• `carrier`: the operator the number is currently allocated to. Ported numbers reflect the *current* carrier, not the original.
• `line_type`: mobile, landline, or voip. The single most useful field for risk.
• `voip`: a convenience boolean for the most common risk case.
• `prefix_type`: the numbering-plan classification (e.g. CLEC), which often reveals VoIP routing even when the carrier name looks ordinary.
• `prepaid`: whether the line is prepaid; cheap and anonymous, so weighted higher in fraud models.
• `country_code` / `state`: geographic context for mismatch and velocity checks.

Reading line type

Mobile numbers carry the most accountability, they're tied to SIMs, contracts, and (often) identity checks by the carrier. Landlines are low-risk but rare in consumer signups. VoIP is the wildcard: convenient for real users, indispensable for fraudsters. prefix_type: CLEC frequently indicates a competitive carrier reselling VoIP, so it's worth watching even when line_type looks benign.

{
  "phone_features": {
    "country_code": "+1",
    "carrier": "BANDWIDTH.COM CLEC, LLC",
    "state": "MD",
    "prefix_type": "CLEC",
    "line_type": "voip",
    "voip": true,
    "prepaid": false
  }
}

Putting the fields to work

No single field is a verdict. A prepaid mobile from a major carrier is unremarkable; a prepaid VoIP number on a CLEC block signing up from a datacenter IP is not. Feed these fields into your risk model as weighted inputs, and let the combination, not any one flag, drive the decision.