23 terms
Phone verification glossary
Short, accurate definitions of the terms you meet when an app asks for a phone number — from OTP and 2FA to non-VoIP numbers, HLR lookups, E.164 formatting, short codes, SIM swaps and A2P messaging. Each entry explains how the thing works and why it matters for SMS verification.
Updated By PhoneBorn TeamEditorial policy
All terms
2
- 2FA (two-factor authentication)
- 2FA (two-factor authentication) is a login method that requires two different kinds of evidence of identity — typically something you know, such as a password, plus something you have, such as a phone or security key — before access is granted.
A
- A2P SMS (application-to-person)
- A2P SMS (application-to-person SMS) is text messaging sent automatically by a software application or business system to individual people, such as verification codes, alerts, reminders and notifications.
B
- Burner number
- A burner number is a secondary phone number a person uses for a limited time or a specific purpose to keep their main number private, with the intention of discarding it when it is no longer needed.
C
- Carrier lookup
- A carrier lookup is a query that returns information about a phone number's network, typically the current carrier, the line type (mobile, landline or VoIP) and whether the number has been ported from its original operator.
D
- DID (direct inward dialing)
- A DID (direct inward dialing) number is a phone number that a carrier routes into a private branch exchange (PBX) or VoIP phone system, which then delivers the call directly to a specific extension, user, queue or application.
- Disposable number
- A disposable number is a short-lived phone number used to receive one or a few messages, such as a verification code, and then abandoned, so it is not linked to the user's permanent identity.
E
- E.164
- E.164 is the ITU-T international public telecommunication numbering plan, which defines phone numbers as a country code followed by a national significant number, up to 15 digits in total, conventionally written with a leading plus sign and no spaces or trunk prefix (for example +14155550123).
- eSIM
- An eSIM (embedded SIM, or eUICC) is a SIM chip built into a device that can download and store mobile operator profiles over the air using the GSMA's remote SIM provisioning standard, replacing the need to insert a physical SIM card.
H
- HLR lookup
- An HLR lookup is a real-time query to the Home Location Register — the central subscriber database of a GSM/3GPP mobile network — that reports whether a mobile number is valid and active, which network it belongs to, and whether it has been ported or is roaming.
K
- KYC (know your customer)
- KYC (know your customer) is the process by which a business verifies a customer's identity, typically by collecting and checking their name, date of birth, address and government-issued ID, before or while providing a service.
M
- MSISDN
- An MSISDN (Mobile Station International Subscriber Directory Number) is the full international telephone number that identifies a mobile subscription on a GSM/3GPP network — in everyday terms, the mobile phone number people dial to reach you.
N
- Non-VoIP number
- A non-VoIP number is a phone number assigned by a mobile network operator to a SIM-based mobile line, rather than by an internet calling (VoIP) provider, so carrier databases classify it as a mobile number.
- Number recycling
- Number recycling is the practice of a mobile carrier reassigning a phone number that was deactivated or abandoned to a new subscriber after an aging period, whose length varies by carrier and country.
O
- OTP (one-time password)
- An OTP (one-time password) is a short, automatically generated code that is valid for a single login, transaction or verification step and expires after it is used or after a short time window.
P
- P2P SMS (person-to-person)
- P2P SMS (person-to-person SMS) is text messaging exchanged directly between individual people, typically conversational, low-volume and sent manually from one personal phone number to another.
R
- Real mobile number
- A real mobile number is a phone number allocated from a mobile network operator's numbering range and served by that network, so carrier and HLR lookups report its line type as mobile rather than VoIP or fixed-line.
S
- Sender ID
- A sender ID is the name or number displayed as the originator of an SMS; in its alphanumeric form it is a brand label of up to 11 characters (such as "MyBank") that replaces the phone number and usually cannot be replied to.
- Short code
- A short code is an abbreviated phone number, usually 5 or 6 digits in the US and similar lengths elsewhere, that businesses use to send and receive high-volume application-to-person text messages such as verification codes, alerts and opt-in campaigns.
- SIM swap
- A SIM swap is the transfer of a mobile phone number from one SIM card or eSIM profile to another; SIM swap fraud is when a criminal gets an operator to make that transfer without the owner's consent in order to receive their calls and SMS codes.
- SMS rate limiting
- SMS rate limiting is a control that caps how many text messages a service, carrier or number can send or receive within a set time window, used to prevent abuse, fraud and network overload.
- SMS verification
- SMS verification is a process in which a service sends a one-time code by text message to a phone number and asks the user to enter it, proving that the user can receive messages on that number at that moment.
V
- Virtual number
- A virtual number is a phone number that is not tied to a physical SIM card in a specific handset and is instead delivered through software, most often over VoIP, so calls and texts reach an app, browser or phone system.
- VoIP number
- A VoIP number is a phone number whose calls and messages are carried over the internet by a Voice over Internet Protocol provider rather than over a SIM-based mobile line, so it is not tied to a physical SIM or device.
Keep reading
Related guides
From definitions to a working number.
Real mobile numbers in 200 countries with SMS and calls, or single-use OTP numbers for one code. Email-only sign-up, crypto payments.