Glossary · definition
What is a VoIP number? VoIP vs non-VoIP explained
A VoIP number is a regular-looking phone number whose calls and texts travel over the internet instead of through a SIM card on a mobile network. Millions of people and businesses use them every day. They also explain one of the most common verification errors: 'This number cannot be used.' Here is how VoIP numbers work and why some apps treat them differently.
Quick answer
What is a VoIP number?
A VoIP number is a phone number provided by an internet calling service instead of a mobile carrier SIM. Calls and texts travel as data, so you can use it in an app or browser on any device. Google Voice and business phone systems are common examples. Some apps reject VoIP numbers during SMS verification to limit fake accounts.
What does VoIP mean?
VoIP stands for Voice over Internet Protocol. Instead of a radio link between your SIM card and a cell tower, your voice and messages are packaged as internet data. A VoIP number is the phone number attached to such a service. It looks exactly like any other number, with a normal country code and area code, and it can call and text ordinary phones.
When a VoIP service connects to the regular phone network so you can call any number and receive calls from anyone, US regulators call it interconnected VoIP. That is why your VoIP number can receive a text from your bank: the message enters the phone network as usual and is handed to the VoIP provider at the end.
What is the difference between fixed and non-fixed VoIP?
Line-type databases, which apps query before they send a code, usually split VoIP into two groups. Twilio's Lookup Line Type Intelligence documentation, for example, defines fixed VoIP as a virtual number associated with a physical device or address, such as a cable company home phone, and non-fixed VoIP as a number obtained online without a physical device, naming Google Voice as an example.
The distinction matters because non-fixed VoIP numbers are quick to create in large quantities, so fraud teams treat them as higher risk. Fixed VoIP, typically a home or office line, is usually treated more like a landline.
VoIP vs non-VoIP: how do they compare?
'Non-VoIP' is shorthand for a number issued by a mobile network operator and tied to a SIM or eSIM. The table summarizes the practical differences. See /glossary/non-voip-number for what sellers mean by the term.
| VoIP number | Non-VoIP (mobile) number | |
|---|---|---|
| Who issues it | Internet calling provider | Mobile network operator |
| Needs a SIM or eSIM | No | Yes |
| Works over | Any internet connection, in an app or browser | The carrier's cellular network |
| How fast to get one | Minutes, online | Usually requires a plan or prepaid SIM |
| Shown by line-type lookups as | Fixed VoIP or non-fixed VoIP | Mobile |
| Accepted for SMS verification | Varies; some apps refuse it | Accepted by most apps |
| Short codes (5–6 digit senders) | Often not supported | Usually supported |
Why do some apps reject VoIP numbers?
Phone verification exists to make each account cost something real. If a number takes seconds to create online, it adds little friction, so many apps check the line type first and refuse non-fixed VoIP. When that happens, the app never sends the code and shows a message such as 'This phone number can't be used for verification.'
Security guidance has pushed in the same direction. NIST SP 800-63B (2017) stated that methods which do not prove possession of a specific device, such as VoIP, shall not be used for out-of-band authentication. The current version, SP 800-63B-4 (August 2025), keeps phone-network delivery as a 'restricted' method that services should back up with alternatives. Each app sets its own policy, and it can change without notice.
What are the pros and cons of a VoIP number?
VoIP numbers are excellent for what they were built for: calling and texting from any device, sharing a business line across a team, keeping a number when you move. They are less reliable as an identity anchor.
- Pro: works on laptops, tablets and phones without a SIM.
- Pro: easy to add a second number for work or online listings.
- Pro: often cheaper than a second mobile plan.
- Con: some apps and banks refuse it for verification or 2FA.
- Con: short-code texts from services may not be delivered.
- Con: if the provider account is lost or closed, the number may be gone.
Are TempSMSVerify numbers VoIP?
TempSMSVerify sources numbers in 140+ countries from established line providers and shows live stock per app and country. We do not promise a specific line type for every number, because line types differ by provider and country, and the line-type databases apps use do not always agree with each other.
What we do promise is the billing rule: your balance is frozen on purchase and charged only if the SMS arrives. If an app rejects a number and no code comes in, you are refunded automatically and can try another country. See /how-it-works and /refund-policy.
FAQ
VoIP number: FAQ
Is Google Voice a VoIP number?
Yes. Google Voice numbers are delivered over the internet, and line-type services such as Twilio's Lookup list Google Voice as non-fixed VoIP. That is why some apps refuse Google Voice numbers at sign-up. Even Google Voice asks you to link a US mobile number that is not another Google Voice number.
How can I tell if a number is VoIP?
You cannot tell from the digits alone. Apps use carrier and line-type lookup services that check which provider the number belongs to and classify it as mobile, landline, fixed VoIP or non-fixed VoIP. Several online lookup tools offer the same check, though results can differ because each relies on its own data.
Can a VoIP number receive SMS verification codes?
Often, yes, if the app is willing to send to it and the sender is a regular long number. Problems come from apps that refuse VoIP line types before sending and from short-code senders that many VoIP providers do not support. If the app rejects the number, no code is sent at all.
Is a VoIP number safe for two-factor authentication?
It is not ideal. If the provider account is compromised or closed, you can lose access to your codes, and many services refuse VoIP for 2FA anyway. For important accounts, use a passkey, security key or authenticator app, and keep any phone number only as a backup.
Is it legal to use a VoIP number?
Yes. VoIP numbers are ordinary, regulated phone numbers used by households and businesses worldwide. What matters is how you use them: follow each app's terms, verify only your own accounts, and never use a number to deceive or harass anyone. Our rules are in the /acceptable-use policy.
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