How to check whether a phone number is VOIP or a real mobile

An applicant's phone number looks like any other: ten digits, a familiar area code. Whether it is a mobile on a real carrier, a landline, or a number provisioned in seconds through a VOIP app is not visible in the digits. It is visible in the public records of who the number was issued to, and in the private records of where it has been moved since. Here is how each check works, what it can and cannot tell you, and how to do the free one in a few seconds.

What does not work: the area code

In North America the area code says where a number was issued, roughly, and nothing about what kind of line it is. Mobiles, landlines and VOIP numbers share the same area codes and the same exchanges. There is no mobile prefix of the kind the UK or India has. Calling the number does not help either: a VOIP number rings, takes voicemail and receives texts exactly like a mobile.

What works for free: the block holder

Every North American number sits in a thousands-block, the first seven digits, and each block is assigned to exactly one carrier by the North American Numbering Plan Administrator. The assignments are public. NANPA publishes a thousands-block report and a central-office-code (exchange) report at reports.nanpa.com/public/, refreshed daily, and the "Assigned To" column is the carrier the block was issued to.

That column is the check. A block assigned to T-Mobile, AT&T, Verizon Wireless or a regional carrier is an ordinary phone. A block assigned to Bandwidth, Onvoy, Inteliquent, Telnyx, Twilio, Peerless, Level 3 or one of the other VOIP wholesalers is a number that was provisioned by API to a VOIP platform, a dialler or an app, and almost nobody's personal phone lives there. If no carrier holds the block or its exchange, the number cannot currently ring anywhere; it is a typo or made up.

To do it by hand: download the thousands-block report, find the row for the number's area code, exchange and first digit of the line (415-555-0 for 415-555-0123), and read the holder. The free number lookup on this site does the same thing from a copy of the same reports, with the holder name sorted into a verdict:

• VOIP wholesaler number. The block holder is on the wholesaler list.
• Carrier number. A mobile or landline carrier. The usual answer for a personal phone.
• Unassigned block. Nobody holds it.

The result also says whether the answer came from the thousands-block record or, when the block is not individually assigned, from the exchange record. Nothing is stored; the number is looked up and forgotten.

What the public records cannot see: ported numbers

Numbers move. A person who switches from T-Mobile to Verizon keeps the number, and a person who moves their old mobile number into Google Voice keeps it too. Porting does not change the block record: the thousands-block stays assigned to the carrier it was issued to. Where a number currently lives is held in the porting database, which is private and reachable only through paid lookups.

So the public check misreads in both directions, and it helps to know which way:

• A mobile number ported into a VOIP app reads as a mobile. Someone who moved their long-standing T-Mobile number into Google Voice or a business VOIP line will show as T-Mobile. The check misses them. For screening, that is the right miss: the number is a real identity's number that has been in their hands for years.
• A wholesaler number ported to a mobile carrier reads as VOIP. This is the false positive to keep in mind. It is uncommon, because people rarely start on a wholesaler number, but it happens, and it is why a wholesaler verdict should put a candidate in a review pile rather than a reject pile.

Google Voice is the common innocent case. Its numbers are drawn from blocks held by wholesalers such as Bandwidth, so in the public record a Google Voice number is indistinguishable from any other wholesaler number. Plenty of real people use Google Voice for job applications to keep their personal number private. Treat the verdict as one signal and look at the rest of the application.

What works for money: a line-type lookup

Carrier and line-type APIs (Twilio Lookup, Telnyx, and others sold to fraud and messaging teams) query the live routing data, so they see the current carrier after porting and return a line type such as mobile, landline or non-fixed VOIP. They are priced per lookup and need an account and some code. ApplySift's wholesaler check was tuned against one such API on a real applicant pool and agreed with its VOIP verdict on 99% of 1,416 numbers; the figure and the caveats are on the signals page. For a single number the free block check is almost always enough. For a thousand numbers the public check costs nothing and the paid one costs real money, and they agree nearly all the time.

Which to use

Reading the answer on an application

A wholesaler number alone means review, not reject. Combined with a fresh Outlook address, a handle full of digits, or the same number on another application, it is close to conclusive, which is what the VOIP numbers guide is about. And if you have a whole posting's worth of applicants rather than one, uploading the export checks every number at once alongside the email and duplicate signals, and the summary is free.