What Is a VoIP Number, and How Do You Check If a Number Is VoIP?

A VoIP number is a real phone number that sends calls and texts over the internet instead of a mobile network or copper phone line, so anyone can call it like any other number, and texting works when the provider supports it. Some lookups label it "fixed VoIP" (tied to an address, like a home phone service) or "non-fixed VoIP" (set up online, like many second number apps), and a few sites refuse the non-fixed kind for verification codes.

This guide is for anyone with, or thinking about, a second number app on an iPhone or Android phone, and for anyone who just saw "VoIP numbers not accepted" on a sign-up form. It explains what a VoIP number is, how to check one, and why some sites say no.

What is a VoIP number?

VoIP stands for voice over internet protocol. According to the FCC, VoIP converts your voice into a digital signal that travels over the internet. If you are calling a regular phone number, the signal is converted into a regular telephone signal before it reaches the other end, so the person you call needs nothing special.

In practice, a call starts in your phone app, travels over the internet, and arrives as a normal call to any phone.

You have probably met VoIP numbers already:

• A home phone service from an internet or cable provider: the phone rings like a traditional one, but the call runs over your broadband connection.
• Office desk phones that plug into the internet connection.
• Second number apps on iPhone and Android, which use Wi-Fi or mobile data.

Is a VoIP number a real phone number?

Yes. A VoIP number is dialed like any other number, and people can call it from a mobile or a landline. The FCC notes you may be able to call anyone who has a telephone number.

Texts depend on the provider. Twilio's line type documentation says a mobile number generally can receive SMS and a landline generally cannot, so it is worth checking that your provider supports texting. What differs about a VoIP number is how the call travels, not the number itself.

What is the difference between fixed and non-fixed VoIP?

In plain words:

• Fixed VoIP: tied to an address, like home phone service.
• Non-fixed VoIP: set up online, like many second number apps.

That difference is a main reason some sites accept one and refuse the other.

These two labels come from line type lookups. Twilio's documentation describes fixed VoIP as "a virtual phone number associated with a physical device," with Comcast and Vonage as examples. It describes non-fixed VoIP as "a virtual phone number obtained online without requiring a physical device," with Google Voice as an example. Twilio's blog adds that a fixed VoIP number requires a physical address, so it is generally tied to a specific user or company, while a non-fixed number does not have that requirement.

Is a VoIP number the same as a virtual number?

Mostly, in everyday use. "Virtual number" is a looser phrase, and Twilio's documentation uses "virtual phone number" for both fixed and non-fixed VoIP. When a site says it does not accept virtual or VoIP numbers, it is describing a line type it can look up.

How can you tell if a number is VoIP or mobile?

Here is a simple three step check for US and Canada numbers.

1. Run a carrier lookup. The free areacode.fyi carrier lookup is a free VoIP number lookup for US and Canadian numbers, with no account or key. It matches the number to public numbering records and shows the assigned carrier, the line type and the rate center. It never shows the owner's name, address or live location.
2. Read the line type: wireless or landline/VoIP. The tool shows one combined label for landline and VoIP, because VoIP numbers often sit in landline-type blocks and it cannot promise which one a number is. It cannot tell fixed VoIP from non-fixed VoIP. That split comes from paid line type lookups such as Twilio's. Treat the result as a signal, not proof.
3. Remember: free lookups can miss porting. A free lookup shows the carrier a block of numbers was originally assigned to. If the owner moved the number to another carrier, the current carrier can differ, and areacode.fyi says only a paid, real-time query can see that. Businesses can run those checks too: Twilio's Line Type Intelligence returns types such as mobile, landline, fixed VoIP and non-fixed VoIP, and notes that Canadian numbers need special approval.

The area code alone will not tell you. The free lookup matches the area code plus the next three digits, and the FCC notes that a VoIP provider may let you pick an area code different from where you live. None of this shows who owns a number; for that, see who can trace a second number, and who can't.

Why do some sites refuse VoIP numbers?

There are three reasons:

• Fraud screening. Twilio's blog says VoIP numbers are often correlated with bots, and that non-fixed VoIP, which has no address requirement, is the type its customers usually filter out before sending a one time code.
• Text delivery. Not every line can receive a text, so a site may check the line type first. Twilio's blog notes the same lookup can steer landlines to a voice call instead.
• Older security guidance. NIST's earlier Digital Identity Guidelines, SP 800-63B revision 3, said methods that do not prove possession of a specific device, such as VoIP or email, shall not be used for out-of-band authentication. The final 2025 revision, SP 800-63B-4, lists among its changes that it removes the prohibition on the use of VoIP phone numbers for out-of-band authentication. It still treats codes sent over the phone network (SMS or voice) as a restricted method that carries added risk. Those rules cover government systems, so this does not mean any particular site has changed its policy.

Most services accept second number apps, not all. If a site just rejected your number, here is what to try.

Is a VoIP number safe to use as your second number?

Yes, for everyday calls and texts with people you choose to share it with. Keep your main mobile number for banking and anything you cannot risk losing access to, because a site may refuse a VoIP number at any time. For more on privacy and legality, read are second phone number apps legal and safe.

Emergencies need extra care. The FCC's VoIP and 911 guide says VoIP 911 calls may not connect to the 911 call center serving your current location, may not automatically send your number or location, and may not work during a power outage or internet failure. Keep your main mobile for emergencies, and check how any app handles 911 before you rely on it.

How does Inovo Second Number work?

Inovo Second Number gives you a real second number on the iPhone or Android phone you already have, with no second SIM. Per its FAQ, every number is a real, dialable number issued by a regulated carrier in the country you choose, including the US and Canada, and calls and texts run over Wi-Fi or mobile data. Like other second number apps, its numbers work over the internet, so some lookups will label them VoIP. Which label a lookup shows can vary by lookup service, and we cannot promise how any one site will treat a number. Verification codes arrive from most services, not all. Prices: see in app.

Numbers are tied to active accounts. If a number expires due to inactivity, it is released and cannot be recovered, so keep your account active. To get set up, see how to get a second phone number without a SIM or our guide to getting a second phone number in 2026. Want a number your family abroad can dial locally? See how to call family abroad without an international plan.

FAQ

Is a VoIP number a real phone number?

Yes. It is dialed like any other number, and people can call it from any phone. Texting works if the provider supports SMS. Only the way the call travels differs: over the internet instead of a mobile network or copper line.

How can I tell if a number is VoIP?

Run a carrier lookup. Free tools such as areacode.fyi cover US and Canada numbers and show wireless or landline/VoIP. Results can lag after porting, and the area code alone does not tell you the line type.

What is the difference between fixed and non-fixed VoIP?

Fixed VoIP is tied to an address, like home phone service. Non-fixed VoIP is set up online, like many second number apps.

Why do some websites not accept VoIP numbers?

Some sites screen non-fixed VoIP numbers to cut down on fake accounts, and not every line can receive texts. Most services accept second number apps, not all. If one rejects yours, see why a website won't accept a VoIP number.

Can a VoIP number receive text messages and verification codes?

Yes, if the provider supports SMS. Verification codes arrive from most services, not all.

Can you call 911 from a VoIP number?

It depends on the provider. The FCC requires interconnected VoIP providers to offer 911, but VoIP 911 calls can work differently from mobile calls: they may not reach the call center for your current location or send your number and location automatically. Keep your main mobile for emergencies.

Is a second number app number a VoIP number?

They work over the internet, so some lookups label them VoIP. That does not make them less real for calls and texts with people.

Get a real second number

Inovo Second Number gives you a second number on iPhone and Android for calls and texts over Wi-Fi or mobile data. Prices: see in app.