For SaaS and mobile app teams
Check phone line type at signup
Find out whether a new user’s number is a cell phone, landline, VoIP or fake before you send a verification code. One API call from your backend tells you which numbers can take an SMS, which need a voice call, and which you’d rather not accept.
No card required to start your trial.
Problems a line type check solves
“Our SMS codes go to landlines”
Someone types their office or home number, the text never arrives and they give up. Check first, then send landlines a voice code or ask for a mobile number.
“We pay for texts to fake numbers”
Numbers like 555-555-5555, 123-456-7890 or area codes that don’t exist still cost you a send attempt. Flag fake numbers and stop them at the form.
“One person keeps making new accounts”
Free trials, promo credits and referral bonuses attract repeat signups using free and burner numbers. See when a number is VoIP and which app it comes from, such as Google Voice, TextNow or Burner.
Where it fits in your signup flow
- The user enters a phone number in your web form or app.
- Your server calls the Phone Validator API with that number and gets back its line type, phone company and a fake-number flag.
- Your rules decide the next step. Send the SMS code, offer a voice call, ask for a different number, or flag the signup for review.
- Send the one-time code through your existing SMS or voice provider. The code is still what proves the user has the phone.
Call the API from your server, not from inside your mobile app or browser code. Your API key should never ship to users’ devices.
What the API returns
A Line Type lookup returns one of CELL PHONE, LANDLINE, VOIP, TOLL-FREE, UNKNOWN or FAKE, plus the phone company, the country and a fake-number flag with a reason. For VoIP numbers, the phone company names the app behind the number, such as Google Voice, TextNow or Burner, so you can write rules for specific providers. Illustrative excerpt:
{
"PhoneBasic": {
"LineType": "VOIP",
"PhoneCompany": "GOOGLE VOICE",
"CountryCode": "US",
"FakeNumber": "NO"
}
}Test your integration for free with the demonstration number in the API documentation. U.S., Canadian and Caribbean numbers work with or without a leading 1. Numbers from other countries need their country code.
Should you block VoIP numbers?
It depends on what a fake account costs you. Plenty of real people use VoIP as their main number: remote workers, small businesses, people with a Google Voice number they’ve had for years. Blocking every VoIP number will turn some of them away.
Many teams start softer. They allow VoIP but limit free trial credits, require a card, or send the signup to review. Strict blocking is more common where one person per account really matters, such as marketplaces, payouts, or apps that give credit for new signups. Learn more about VoIP line types.
What a line type check doesn’t do
We check the number, not the person. A cell phone result doesn’t prove the user has that phone, and it doesn’t guarantee a text will be delivered. Keep your one-time code step. Read more about validation vs. verification.
Numbers can move between carriers and line types. Porting information varies by country, and Canadian results may reflect the number’s original assignment. Line type also isn’t permission to send marketing texts. Handle consent separately.
Try it on your signup numbers
Look up a number for free to see the result, then start a trial to call the API from your signup flow. Need to check existing users too? Upload a list and get line types for all of them at once.