SMS verification glossary
The words around phone verification get used loosely. This glossary defines each one in plain English, explains how it works under the hood, and says what it means for your security, with sources and dates so you can check the facts yourself.
Quick answer
What terms should I know before using SMS verification?
Start with six: OTP (a code that works once), 2FA (a second proof besides your password), SMS verification (a code sent by text), SIM swap (a scam that hijacks your number), and VoIP versus non-VoIP numbers (internet lines versus mobile-network lines). Together they explain why apps ask for a phone and when codes fail.
- OOne-time password (OTP)
- A one-time password (OTP) is a short code, usually 4 to 8 digits, that proves who you are for a single login or action and then stops working.
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- TTwo-factor authentication (2FA)
- Two-factor authentication (2FA) is a login method that requires two different kinds of proof, such as a password plus a code from your phone.
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- SSIM swap
- A SIM swap scam is when a criminal convinces your carrier to move your phone number to their SIM card so they receive your calls and verification codes.
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- VVoIP number
- A VoIP number is a phone number delivered over the internet by a software provider rather than tied to a SIM card on a mobile carrier's network.
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- NNon-VoIP number
- A non-VoIP number is a phone number issued by a mobile network operator and tied to a SIM or eSIM, which line-type lookups classify as mobile.
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- SSMS verification
- SMS verification is a check in which a service texts a one-time code to a phone number and you enter it to prove you control that number.
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- VVirtual number
- A virtual number is a phone number you use without putting a SIM card for it in your phone, through an app or website instead.
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- SSMS short code
- An SMS short code is a 5- or 6-digit number businesses use to send texts such as verification codes and alerts within one country.
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- 110DLC (10-digit long code)
- 10DLC means 10-digit long code: an ordinary US phone number registered for business texting, such as verification codes, through The Campaign Registry.
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- CCountry calling code
- A country calling code is the 1- to 3-digit prefix, written after a plus sign, that routes a call or text to a country, such as +1 or +44.
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- EE.164 format
- E.164 is the ITU standard for international phone numbers: a plus sign, country code and national number, no spaces, at most 15 digits.
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- EeSIM
- An eSIM is a SIM built into your phone that you activate by downloading a carrier profile instead of inserting a plastic card.
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- SSMS gateway
- An SMS gateway is a system that sends or receives text messages between software and mobile networks, such as the service that delivers your OTP codes.
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- SSmishing
- Smishing is phishing by text message: a fake SMS that tries to make you tap a link, share a code or pay money.
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