What Does "Ext" Mean in a Phone Number?

"Ext" means extension: a short internal number that reaches a person or department after the main number connects. For example 555-0123 ext. 45.

How to dial an extension

1. Call the main number.
2. Wait for the greeting or menu.
3. Type the extension digits.

Dial it automatically

• Pause (comma): waits a couple of seconds, then dials the extension. Write it as 5550123,45.
• Wait (semicolon): asks you before dialling the extension.

On most phones, long-press * or # or use the keypad menu to add a pause or wait.

Writing it

Can an extension receive texts?

No. Extensions are part of an office phone system. Codes need a full number that can receive SMS.

Extensions in sign-up forms

Most sign-up forms have no box for an extension. Do not add it to the number field, or the number becomes invalid. Use a direct number for verification instead.

FAQ

What does ext mean on a phone number?

Extension: an internal number reached after the main number.

How do I dial an extension on a mobile?

Add a pause (comma) after the main number, then the extension.

Can I receive verification codes on an extension?

No.

Related: how to write a phone number · dial international numbers · US test numbers.