Number Lookup
The industry calls this an LRN query. Same thing.
Send a phone number, get back the carrier that owns it today and whether it's a mobile you can legally text — plus rate center, LATA and ported status, in one call.
Try a query
Enter an 11-digit US number as 1NPANXXXXXX. Sample responses only — no live dip.
GET /api/v1/lrn?tn=12125551234&extended=true&output=json - 2–5 ms
- Typical response
- 100,000
- Queries per second
- United States
- Coverage
- 24/7
- Monitoring, geographically diverse
The number is not what it says it is.
Roughly half of US numbers have changed carrier at least once, and nothing about the number itself changes when they do. A landline that became a mobile looks identical in your database — until you ask.
That one field decides whether a message can arrive at all. Text a landline and it fails, you still pay, and a high failure rate is exactly the signal that gets 10DLC throughput throttled.
What the line type is actually protecting
Screening a list on line_type before a send does two things at once. It stops
you paying for messages that cannot arrive, and it keeps your delivery rate
where carriers want to see it — which is the number they look at when they
decide how much throughput your campaign gets.
Working through registration? Our 10DLC guide covers what carriers check, and the SMS compliance checklist covers consent and STOP handling. This is the data layer underneath both.
The other reasons people ask
Signup validation. A number that is VoIP, freshly ported, or sitting on a carrier known for disposable numbers is not proof of anything on its own — but it is a signal worth having at account creation rather than after.
CRM hygiene. Mobile and landline in one unlabelled field is the normal state of most customer databases. Enriching it once tells you which records can be texted and which have to be called.
Least-cost routing, for the carriers who came for that. Terminating an on-network call as though it were off-network means paying someone else to carry your own traffic. Accurate LNP data routinely takes 20% or more off termination costs.
Two ways to ask
WebAPI for anything outside a live call — list screening, validation at signup, CRM enrichment, billing reconciliation. JSON or XML, and fast enough to sit inside a signup form without anyone noticing.
SIP302 redirect for the call path itself. Your switch sends the INVITE, we
answer 302 Moved Temporarily with the LRN in the Contact header, and your
switch reroutes. No integration work, priced by concurrent queries per second
rather than per lookup.
Interoperability testing is free. We would rather find out your switch disagrees with ours on a lab call than on your traffic.
What comes back
One extended lookup, exactly as the API returns it. Ask for the base response instead and you get the first five.
- "tn""14845550134"
- The number you asked about, echoed back so a batch of answers stays lined up with the batch you sent.
- "lrn""4846090134"
- The Local Routing Number the call should follow — what carriers use for least-cost routing.
- "ocn""6529"
- Operating Company Number — the four-character code for that carrier, for matching against your own records.
- "lec""T-Mobile USA, Inc."
- The carrier that owns the number today, in plain text. Not who issued it years ago.
- "line_type""mobile"
- Landline, mobile or VoIP — the field that decides whether a number can receive SMS at all.
- "rate_center""ALLENTOWN"
- The rate center the number really belongs to, which is not always what its area code suggests.
- "state""PA"
- The state that rate center sits in.
- "lata""226"
- The LATA, where intra- versus inter-LATA changes what a call costs.
- "ported"true
- Whether the number has moved carrier. Roughly half of US numbers have.
Put Number Lookup to work.
Tell us the volume and the format, and whether it runs in a call path or against a list. We'll come back with something itemized.