VoIP vs non-VoIP numbers: which one receives your codes?

What is a non-VoIP number, and how is it different?

A non-VoIP number is a real mobile number issued by a mobile carrier; a VoIP number comes from an internet telephony provider. Both can call and text, but apps can tell them apart. Every phone number belongs to a range, and every range is registered to an operator with a line type: mobile, landline, VoIP or toll-free. Numbering databases and commercial lookup services let anyone check that line type in a fraction of a second.

• A real mobile number is issued by a mobile network operator, in a mobile range. To the rest of the world it looks exactly like the number of a SIM card.
• A VoIP (virtual) number comes from an operator that provides numbers for internet telephony. It works for calls and, in most ranges, for texts — but a lookup identifies it as VoIP.
• A landline or national number belongs to a fixed range. It is great for voice, and texts depend on the country.
• A toll-free number is paid for by the receiver, so callers ring it for free.

None of this changes how a number sounds on a call. It changes how the services you sign up to treat it.

Why apps reject VoIP numbers

Many services send verification codes only to numbers they believe belong to a real person. VoIP numbers are cheap and easy to create in bulk, so fraud teams treat them as a risk signal. Before sending a code, a service may:

• look up the line type and refuse VoIP or landline numbers outright;
• accept the number but send the code from a short code — a 5- or 6-digit sender — that some VoIP routes can’t receive;
• let you sign up, then ask for a different number later, when you try to withdraw funds or recover the account.

The check takes a fraction of a second. Lookup services such as Twilio’s Line Type Intelligence classify any number as mobile, landline, fixed VoIP, non-fixed VoIP, toll-free and more, and a sign-up form can refuse the number before a single code is sent.

Rules differ from one service to the next and change often. The same VoIP number can work with a messaging app and fail with a bank. That is why no honest provider can promise that a number “works with everything”.

Why a number can work today and fail tomorrow

The line type is not the only signal. Services also look at a number’s history. A number that was recently used by someone else may still be attached to their old accounts, and a range known for abuse can be flagged as a whole. Risk rules are updated constantly, so a range that is accepted this month can be refused next month.

Two things reduce that risk. First, a number that isn’t recycled straight away: on Numonym, a released number goes into quarantine before it can be rented again, so the previous user’s accounts have time to fade out. Second, a number you keep: registering once and keeping the number for years is far more reliable than signing up with a fresh number every time.

Mobile, local and VoIP side by side

On Numonym, mobile numbers cost more than local and national ones because mobile ranges are harder to obtain and to keep. See current prices.

Which one should you choose?

• The number will protect accounts — messaging apps, exchanges, email, anything you would need to recover one day: choose a mobile number and keep it for the long run.
• The number is for talking — friends, clients, deliveries, classifieds: a local or national number does the job for less, as long as you don’t need codes from apps.
• The number represents a business — a local or national number too, usually behind a call flow with business hours.

If you use the number for security codes, also think about the long term. Losing access to a recovery number can lock you out of the accounts it protects, so pick a 12- or 24-month rental and read how to protect your accounts from SIM swapping.

What Numonym shows before you pay

Every number card on Numonym tells you, before payment:

• its line type — carrier mobile range, city range or national range, never blurred;
• whether it handles calls and texts in each direction, and short codes;
• whether it can be ported out later;
• whether people will see your number when you call them from abroad.

Instead of promising that a number works everywhere, we let you swap it for free within 72 hours if it doesn’t work for what you bought it for.

When the code comes by phone call

Some services offer to read the code out loud in a phone call, especially when a text doesn’t arrive. That works with any number type that receives calls, including landline, national and many VoIP numbers.

On Numonym, voicemail is transcribed automatically, and codes read aloud are detected and shown with a copy button — just like codes received by SMS. You can also answer the call live in your browser.