Last updated
March 15, 2024

Mastering Phone Number Identity Verification: A Comprehensive Guide

Brian Wu

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What is Phone Number Validation?

Phone number validation is a process that ensures the phone number provided by a user is in the correct format, active, and capable of receiving text messages or calls. This is a key step in identity verification systems to prevent fraud and to ascertain that communications reach the intended recipient.

This ties directly into digital identity verification, adding a layer of security to processes like account creation or transaction authorization. Risk assessment through phone validation goes further by evaluating phone-related attributes and signals, determining the level of risk associated with a mobile phone number to inform subsequent security measures or authentication steps. 

How Does Phone Number Verification Work?

Phone verification works by employing different methods to ensure that a phone number is legitimate and belongs to the person claiming it:

OTP and SMS Verification: This is the most common form of phone verification. A one-time password (OTP) is sent via SMS to the phone number provided during an online transaction or account registration. The user must enter this OTP back into the application to confirm ownership of the mobile phone number. This method is effective because it requires physical access to the phone to receive the text message.

SIM-based and Silent Mobile Verification: This method is more secure and less intrusive, involving a background check that confirms the phone number is currently active on the device. It can validate the device's SIM card information without sending an OTP, thus preventing OTP interception fraud.

Database and Carrier Checks: These checks involve querying databases to validate the phone number's format, determining if it is currently in service, and ensuring it is not on any blocklists. Additionally, they can verify the carrier details to confirm that the phone number is on a legitimate network and hasn't been ported in a way that suggests fraudulent activity.

Here’s a video on how scammers can use your phone number to send fake verification codes.

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List of Benefits and Drawbacks of Phone Number Verification


  • Enhanced security through user authentication
  • Reduction in fraud and unauthorized access
  • Improved user trust and data points accuracy


  • Potential for OTP (One Time Password) interception or fraud (especially with SMS and voice)
  • Dependence on user access to their device or network
  • Possible user inconvenience or friction, impacting the user experience

How to Verify a Phone Number

To verify identity of a mobile phone number, you typically go through a process that confirms the number is active and belongs to the user. Here's a general step-by-step guide you can follow, which aligns with best practices across various platforms and service providers:

  1. Request Verification: Initiate the phone carrier verification process within your application or on the service platform, which often starts with the user entering their phone number.
  1. Send a Code: The service provider sends a unique One-Time Password (OTP), usually via SMS, to the phone number provided.
  1. Enter the Code: The user receives the OTP and enters it back into the application or service to validate their phone number.
  1. Confirm Verification: Once the code is correctly entered, the service confirms the phone number is verified.

For a more secure phone validation, you can implement:

Silent Mobile and SIM-based Verification: This is less intrusive and confirms that the phone number is active on the device without the need for an OTP.

Carrier and Database Checks: These involve verifying the phone number against databases to ensure it is valid and not associated with fraudulent activities.


Phone Verification APIs and Their Integration

Abstract API

Offers comprehensive phone number validation and verification solutions functionality, supporting international numbers with detailed information on carrier, line type, and geographical data. Integration requires an API key, and developers can make HTTP requests to validate numbers, receiving JSON-formatted responses.


Provides a straightforward API for phone number validation, covering over 200 countries. Developers need to sign up, obtain an API key, and use it in their HTTP request for accessing the service. The response includes number validity, country code, and line type among other details.


The Number Verification API from apilayer offers extensive services similar to the above, with support for global numbers, carrier information, and number type detection. Integration involves obtaining an API key and making authenticated requests to their endpoint.

How to Verify a Phone Number With an API (Abstract)

Abstract's Phone Number Validation and Verification API is a tool designed to ensure that phone numbers collected are valid and belong to real users. It helps in maintaining clean contact information lists by screening out fake, disposable, or low-quality numbers. 

This API supports phone numbers from over 190 countries and provides detailed information, including the carrier and line type—whether it's a landline, mobile, or VOIP. It can also deliver geographic data like the country, region, or city. 

All interactions with this API are secured with bank-level SSL encryption to protect data integrity. For more detailed instructions on integrating and using this API, check out the Abstract API website.

Verifying a phone number with the Abstract API involves a few straightforward steps:

1. Sign Up for Abstract API: Create an account on Abstract API and get your unique API key.

2. API Request: Make a GET request to the phone validation endpoint with the phone number and your API key as query parameters.

3. Handle the Response: The API will respond with a JSON object containing the validation results, including whether the number is valid, its risk score, location, carrier, line type, and formatting information.

4. Integrate in Your Application: Use the response in your application logic to verify phone numbers during user sign-up, form submissions, or wherever phone number validation is needed.

Comparison Table of Phone Verification Methods and Their Risk Levels

Phone Verification MethodsRisk LevelsSMS OTPsModerate risk due to susceptibility to SIM swapping and interceptionVoice Call VerificationModerate risk; depends on secure phone lineApp-based Tokens (e.g., Authenticator Apps)Lower risk, with encrypted communication and user interaction requiredPush Notification Verification Lower risk, leveraging encrypted communicationsBiometric Verification Low risk, highly secure, using physical characteristics

Other Use Cases

Abstract's Phone Number Validation and Verification API can be utilized in various use cases beyond just maintaining contact information lists. Some other potential applications include:

Two-factor authentication: Integrating the API for an additional layer of security during login or transaction processes.

Fraud prevention: Identifying and blocking numbers that are commonly associated with fraudulent activities.

Marketing campaigns: Ensuring marketing efforts are not wasted on invalid phone numbers, thus improving the ROI of campaigns.

Customer data analysis: Gaining insights into customer demographics based on the geographic data associated with their phone number.

E-commerce transactions: Verifying phone numbers during checkout to reduce the risk of false transactions and chargebacks.

User registration workflows: Improving user experience by automating phone number format correction and validation.


Gaining expertise in phone number identity verification is essential to preventing an identity fraud and guaranteeing real user interaction. Businesses can securely safeguard their operational frameworks, expedite their communication strategies, and confidently authenticate user identities with the help of services that provide Phone Number Validation and Verification API. 

In our increasingly digital world, this guide emphasizes the importance of phone verification as a means of achieving strong security protocols and enhanced data integrity. 



"When conducting online transactions, lookup a sign that the site is secure such as a lock icon on the browser’s status bar or a 'https:' URL whereby the 's' stands for 'secure' rather than a 'http:'. Also, beware of phone phishing schemes. Do not divulge personal information over the phone unless you initiate the call. Be cautious of emails that ask you to call a phone number to update your account information as well." - Identity Theft Killer (Are You Phishing for Trouble?)


Difference Between Phone Number Validation and Verification

Validation checks if a phone number is properly formatted and potentially active, without verifying who it belongs to. Verification goes further, confirming the phone number is actively used by the person attempting to use it, typically through an OTP.

Can Phone Verification Be Bypassed by Fraudsters?

Yes, fraudsters can bypass phone verification through methods like SIM swapping, using virtual phone numbers, or intercepting SMS codes. Enhanced security measures and constant vigilance are necessary to combat these tactics.

Is Phone Verification Compliant with Privacy Regulations?

Yes, when properly implemented, phone verification can comply with privacy regulations such as GDPR, CCPA, and others. It must involve clear user consent, secure data handling, and adherence to principles like data points minimization and purpose limitation.

Brian Wu
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