# What is National Format

Twilio's Lookup API returns phone numbers in *national format*, a string containing the phone number formatted according to the most common style in the associated country.

## North American Numbers

For example, phone numbers in the United States are defined by the [North American Numbering Plan](https://en.wikipedia.org/wiki/North_American_Numbering_Plan) (NANP) as ten-digit numbers consisting of:

1. A three-digit Numbering Plan Area \[local link] (NPA) code, commonly called an area code
2. A seven-digit local number. The format is usually represented as NXX-NXX-XXXX where N is any digit from 2 through 9 and X is any digit from 0 through 9.

The national format returned by Twilio for NANP numbers is therefore (NXX) NXX-XXXX.