Glossary SMS verification, term by term.
30 short, plain-language definitions of the vocabulary behind phone verification: numbers, routes, codes, and checks.
- A2P SMS Application-to-person SMS: messages sent by software, such as verification codes and alerts, rather than by another person.
- Activation window The countdown during which a rented number stays allocated to you and listens for the verification SMS, usually 5 to 20 minutes.
- Country calling code The 1-3 digit prefix that routes a number to its country, such as +1 for the United States and Canada, +49 for Germany, +81 for Japan.
- Delivery report (DLR) The carrier's confirmation that an SMS reached the destination handset, or the error code explaining why the message never got there.
- Disposable number A number meant to be abandoned after brief use, especially the free public numbers whose inboxes anyone can read on a receive-SMS website.
- E.164 The international standard format for phone numbers: a plus sign, the country code, then the subscriber number, up to 15 digits.
- Flash call Verification by a brief incoming call where the last digits of the calling number are the code, so the call never needs answering.
- Gray route An unofficial SMS delivery path that dodges carrier fees for business traffic, cheaper for the sender and heavily filtered on arrival.
- HLR lookup A live query to a carrier's Home Location Register that reveals whether a mobile number is active and which network it belongs to.
- KYC (know your customer) Identity verification that regulated services must perform before serving a customer, typically a government ID document plus a live selfie.
- Long code A standard-length phone number used for SMS, such as ten digits in the United States, and what you rent when you buy a verification number.
- Mobile network operator (MNO) A company that owns mobile network infrastructure and issues phone numbers from its allocated ranges, such as Vodafone or T-Mobile.
- MVNO A mobile virtual network operator that sells service under its own brand using another operator's physical network, such as Giffgaff on O2.
- Non-VoIP number A phone number from a real mobile carrier range rather than an internet telephony provider, which is what most platforms require for SMS codes.
- Number activation One rental of a number for one verification: the number is allocated to you, receives the code, then returns to the provider's pool.
- Number pooling Recycling numbers through a shared pool, so a number that finished one activation later serves another customer for a different service.
- OTP (one-time password) A short code valid for a single login or verification, typically 4-8 digits delivered by SMS, voice call, or generated by an app.
- P2P SMS Person-to-person SMS: ordinary texting between two individual subscribers, priced and filtered differently from application traffic.
- Phone number reputation A platform's internal risk score for a phone number, based on its range, history, and how many accounts it has verified.
- Sender ID The name or number an SMS appears to come from, such as an eleven-character brand name or a short code, instead of an ordinary phone number.
- Short code A 4-6 digit number businesses use to send high-volume SMS such as verification codes; it can send but is not an ordinary subscriber line.
- SIM farm Hardware holding hundreds of SIM cards to send or receive SMS in bulk, a major source of both supply and abuse in the SMS market.
- SMS gateway The system that moves messages between the internet and carrier networks, connecting an application's verification codes to the SMS world.
- SMS verification Confirming that a user controls a phone number by sending a one-time code by SMS and asking them to type it back into the sign-up form.
- Temporary phone number A number used for a short period, from minutes for a single verification to weeks for a rental, then returned to the provider's pool.
- TOTP (time-based one-time password) A one-time code generated on your device from a shared secret and the current time, used by authenticator apps like Google Authenticator.
- Two-factor authentication (2FA) Requiring a second proof of identity beyond the password, such as an SMS code, an authenticator app, or a hardware security key.
- Virtual phone number A real phone number used without a physical SIM card in your device, typically rented briefly to receive an SMS verification code.
- Voice OTP A one-time code read aloud in an automated phone call instead of delivered by SMS, used as a fallback when text routes are filtered.
- VoIP number A number issued by an internet telephony service rather than a mobile carrier, and the kind most platforms refuse for SMS verification.
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