What is a short code? Who sends your verification texts
In short
- Codes come from a short code (five digits in the UK, five or six in the US), an ordinary number, or a sender name of up to 11 characters.
- Short codes only work in their own country, so codes from abroad come from an ordinary number or a sender name.
- Sender names can be faked, so a scam text can land in the same thread as real ones from your bank.
Look at who sent your last verification code. It came from one of three kinds of sender, and each behaves a little differently.
Short codes
Short numbers that companies text from. In the UK they’re five digits, shared by all the main networks and allocated through short-codes.com, which the networks run. In the US they’re five or six digits, leased through the US Short Code Registry.
- A short code only works in its own country: a US short code can’t text a UK number.
- Some prepaid plans can’t receive them, Amazon Web Services notes.
- Networks can block them. See networks blocking verification texts.
You never need to reply to a verification text. Replying to a short code can cost money, as some run paid services outside your allowance.
Ordinary numbers
Long numbers, like any mobile number, sometimes from another country. Unlike short codes, they can text across borders. Uber, for example, says its codes can come from a foreign number, so don’t block those.
Sender names
A name instead of a number, such as an app’s or a bank’s, up to 11 characters long. They’re common in the UK and Europe, but texts to US numbers can’t show one, so there codes come from short codes or numbers, including toll-free ones.
Fake sender names
Criminals can change the sender name on a text to copy a real one, so a fake can appear in the same thread as genuine messages from your bank. In the UK, the Mobile Ecosystem Forum runs an SMS SenderID Protection Registry: brands register their names, and the messaging firms that take part block texts using them from anyone else, along with look-alike spellings.
It cuts the fakes but can’t stop them all. Treat any text that asks for a code, a payment or a login as suspect, whatever the sender says. See the verification code scam.
Using a one-time number
Which sender an app uses, and whether it sends to a given number, is up to the app. If a number from ReserveSMS gets no code within 20 minutes, the money goes back to your balance; ours start at $1.
Common questions
What is a short code text?
A text from a short number, five digits in the UK and five or six in the US, that companies use for codes and alerts.
Why did my verification code come from a foreign number?
Short codes only work in their own country, so apps also send from ordinary numbers, sometimes abroad. Uber says its codes can come from one.
Can a text showing my bank’s name be fake?
Yes. Sender names can be faked, so a scam can land in the same thread as real texts. Never share a code a text or caller asks for.