United States Postal Code Format Guide
US ZIP Codes use five digits; an optional four-digit ZIP+4 suffix narrows delivery to a smaller segment. The first digits identify broad regions, and city/state/ZIP values should be kept consistent.
Standard format
NNNNN or NNNNN-NNNN
Example
10001
Implementation and validation notes
US ZIP Codes use five digits; an optional four-digit ZIP+4 suffix narrows delivery to a smaller segment. The first digits identify broad regions, and city/state/ZIP values should be kept consistent.
Validate required state, character set, length, and syntax on the client, then repeat validation on the server. Preserve the original input and normalize into a separate field; never truncate local scripts, compound names, or leading zeroes to fit a single Western assumption.
This guide describes common formats rather than an official registry and cannot enumerate every exception. Generated output is for testing only, not delivery, calling, identity verification, or real account activity.
Related resources
Frequently asked questions
What is the standard United States postal code format?
A common representation is NNNNN or NNNNN-NNNN, for example 10001. US ZIP Codes use five digits; an optional four-digit ZIP+4 suffix narrows delivery to a smaller segment. The first digits identify broad regions, and city/state/ZIP values should be kept consistent.
How should United States postal code test data be stored?
Store the original value as a string so leading zeroes, spaces, hyphens, accents, and local scripts are preserved. Use a separate normalized field for search.
Does correct formatting prove the data is real?
No. Syntax validation cannot prove an address is deliverable, a number is assigned, or a name belongs to a real person.