You saw the word “VoIP” next to a phone number and want to know what it means. This post explains what a VoIP number is, the two kinds, how apps see a number’s line type, and how the TripoSIM US number handles verification codes.
What is a VoIP number?
VoIP stands for Voice over Internet Protocol. A VoIP number is a normal-looking phone number, such as a US +1 number, whose calls and texts travel over the internet rather than through a mobile carrier’s cell network or a copper landline.
In US rules, the FCC defines an interconnected VoIP service as one that offers real-time two-way voice, needs a broadband connection, uses internet-compatible equipment and can make and receive calls with the ordinary phone network (47 CFR 9.3). In plain words: it behaves like a phone number, but it runs on the internet.
Fixed vs non-fixed VoIP: what is the difference?
The FCC’s rules split VoIP into two kinds. A non-fixed service is one “capable of being used from more than one location” (47 CFR 9.11). A fixed service is tied to one place.
Lookup providers use the same split. Twilio’s line-type documentation describes them like this (Twilio Docs):
| Line type | What it means | Twilio’s examples |
|---|---|---|
| Mobile | A carrier mobile number that generally can receive SMS | Your phone carrier’s SIM number |
| Landline | A carrier fixed line that generally can’t receive SMS | A home phone line |
| Fixed VoIP | “A virtual phone number associated with a physical device” | Comcast, Vonage |
| Non-fixed VoIP | “A virtual phone number obtained online without requiring a physical device” | Google Voice, Enflick |
When people search “non-VoIP number”, they usually mean the first two rows: a number a lookup labels as a carrier mobile or landline.
How do apps know my number is VoIP?
They look it up. Many services query a phone number intelligence database with your number. The answer includes the line type (mobile, landline, fixed VoIP, non-fixed VoIP and others) and often the carrier name. Twilio, for example, sells this as a paid feature called Line Type Intelligence, and returns “unknown” when it cannot tell.
So “why is my number VoIP?” usually has one of three answers:
- It really is VoIP. App numbers, Google Voice and similar services sit on internet-based networks.
- It was ported or recycled. A number that moved between providers can carry an old label.
- The database is wrong. Lookups are not perfect. If you pay a mobile carrier for a SIM and the number shows as VoIP, ask the carrier how the number is registered.
The area code plays no part. The three digits after +1 say nothing about the line type.
Does the TripoSIM VoIP number receive verification codes?
Yes. The TripoSIM US Virtual Number is a VoIP number: it works through the TripoSIM app over Wi-Fi or mobile data, it is not a carrier SIM or mobile line, and it can be used from anywhere you have internet, which matches the non-fixed description above.
It receives verification codes (OTP SMS) from apps, including WhatsApp and WhatsApp Business. TripoSIM tested 22 apps from October 3 to 18, 2026: WhatsApp on October 13, 2026, WhatsApp Business on October 18, 2026, and apps such as Google, PayPal, Upwork and Fiverr on October 3, 2026. That list shows examples, not a limit. Look up any app in the app check tool, or read our guide to a US number for verification codes.
What if a code does not arrive right away?
- Check the number. Pick United States (+1) and type the 10 digits, with no extra leading 1 or 0.
- Wait for the timer. Codes can take a minute or two. Request it once, then wait before asking again.
- Use the voice call option if the app offers one. The TripoSIM number takes incoming calls and has voicemail.
- Keep the app connected. The number needs the TripoSIM app and an internet connection to receive texts and calls.
- Contact TripoSIM support from the app or TripoSIM’s contact page if it still does not arrive.
Where does the TripoSIM number fit?
It is a US number for calls with US contacts, voicemail, receiving texts from US and Canadian senders and verification codes from apps, including WhatsApp, while you live abroad. It receives texts but cannot send them, and it cannot call 911. The number type comparison sets out how it differs from a carrier line and a travel data eSIM.
Bottom line
A VoIP number is a phone number that runs over the internet, and apps can see its line type through a lookup. The TripoSIM number is a non-fixed VoIP number that receives verification codes from apps, including WhatsApp and WhatsApp Business, so you can use it to sign up and keep your accounts on a US number. See the plans to get one.