The 11 fields and concepts you'll meet in the response — defined in plain English, each with a real example value.
The international standard format for phone numbers, consisting of + sign, country code, and subscriber number with no spaces.
E.164 is defined by the ITU-T and supports up to 15 digits. It uniquely identifies any phone number worldwide and is required by most SMS and VoIP APIs. Example: +14155551234 for a San Francisco number.
Example+14155551234, +442071234567, +819012345678
The numeric prefix identifying a country in international phone numbers (e.g., +1 for US, +44 for UK).
Country codes range from 1 to 3 digits. Some codes are shared—+1 covers all North American Numbering Plan countries including US, Canada, and Caribbean nations. The code is required for E.164 format.
Example+1 (US/Canada), +44 (UK), +91 (India), +81 (Japan)
How phone numbers are written for domestic dialing within a country.
National format includes trunk prefixes and local formatting conventions. US uses (415) 555-1234, UK uses 020 7946 0958. When collecting user input, accept national format but convert to E.164 for storage.
Example(415) 555-1234 (US), 020 7946 0958 (UK)
Classification of a phone number as mobile, landline, VoIP, toll-free, or premium.
Line type determines capabilities—mobile can receive SMS, landlines typically cannot. VoIP numbers may indicate fraud risk. Toll-free and premium numbers have special billing. Validation APIs return line type to help filter numbers appropriately.
Examplemobile, landline, voip, toll_free, premium_rate
A phone number assigned to a wireless cellular device, capable of receiving calls and SMS.
Mobile numbers are ideal for SMS-based verification and two-factor authentication. In most countries, mobile numbers have distinct prefixes. Mobile numbers can be identified through validation APIs that check number ranges and carrier data.
ExampleUS mobile: +1 415 555 1234, UK mobile: +44 7911 123456
A traditional wired telephone connection that typically cannot receive SMS messages.
Landlines are connected via physical cables to the telephone network. While they receive voice calls, SMS delivery to landlines usually fails (though some carriers offer text-to-speech). For SMS verification, offer a voice call alternative for landline users.
ExampleUS landline: +1 212 555 1234 (NYC area code)
Voice over IP—phone numbers that route through the internet rather than traditional phone networks.
VoIP includes services like Google Voice, Skype, and business phone systems. These numbers can often receive SMS but are flagged as higher fraud risk since they're easier to obtain without identity verification. Some services require additional verification for VoIP numbers.
ExampleGoogle Voice numbers, Skype In numbers, business VoIP
The telecommunications company operating a phone number (e.g., Verizon, AT&T, Vodafone).
Carrier information helps with SMS routing optimization and fraud detection. Due to number portability, the current carrier may differ from the original carrier assigned to that number range. Carrier lookup accounts for porting.
ExampleVerizon Wireless, AT&T, T-Mobile, Vodafone
The ability to transfer a phone number from one carrier to another while keeping the same number.
When users switch carriers, they often keep their phone number. This means the number's prefix no longer indicates its carrier. Accurate carrier lookup requires checking portability databases, not just number ranges.
ExampleMoving from Verizon to T-Mobile while keeping +1 415 555 1234
Mobile Network Operator—a carrier that owns and operates wireless network infrastructure.
MNOs like Verizon, AT&T, and Vodafone own cell towers and spectrum licenses. They sell wholesale capacity to MVNOs. Understanding whether a number is on an MNO vs MVNO can affect fraud scoring.
ExampleVerizon, AT&T, T-Mobile, Vodafone
Mobile Virtual Network Operator—a carrier that resells wireless service using another company's network.
MVNOs like Cricket, Boost, and Mint Mobile don't own infrastructure. They lease capacity from MNOs at wholesale rates. MVNO numbers may have slightly different fraud profiles than MNO numbers since some MVNOs have easier signup processes.
ExampleCricket Wireless (AT&T), Boost Mobile (T-Mobile), Mint Mobile
