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ZIP code validator
Check whether a US ZIP code has a valid 5-digit or ZIP+4 format, and see which region the first digit points to.
Input
ZIP code check
—Enter a US ZIP code to check its 5-digit (or ZIP+4) format.
A free ZIP code validator that checks whether a US postal code matches the standard 5-digit or ZIP+4 (9-digit) format and identifies the broad geographic region indicated by the first digit. Format check only — it does not verify the ZIP is currently in service with USPS.
How to validate a ZIP code
- Enter a 5-digit ZIP (e.g. 90210) or a ZIP+4 (e.g. 90210-1234) in the input field.
- The validator checks that the format is exactly 5 digits, or 5 digits + hyphen + 4 digits.
- It maps the first digit to its USPS regional group (0 = New England, 9 = Pacific).
- Result shows valid with the region label, or the specific format error.
US ZIP code structure
USPS ZIP codes are 5-digit numbers introduced in 1963. The first digit identifies a broad national delivery area (0 covers New England through New Jersey; 9 covers California, Alaska, Hawaii, and Pacific territories). The next two digits narrow to a sectional center facility (SCF), and the final two to a specific post office or delivery zone. ZIP+4 adds a 4-digit suffix that identifies a block or delivery route, improving automated sorting precision. This validator checks format only — actual deliverability and current active status require a USPS address verification API.
What format validation does not confirm
- Whether the ZIP code is currently assigned and in service with USPS.
- Whether the ZIP matches a specific city, state, or address.
- Whether the ZIP+4 extension identifies a real delivery point.
- ZIP codes are occasionally retired, split, or reassigned — only USPS records are authoritative.
Frequently asked questions
What does ZIP code validation check?
It confirms the number is exactly 5 digits (or 5+4 for ZIP+4) and identifies the national delivery region from the first digit. It does not confirm the ZIP is active or assigned to a real location.
What do the digits in a ZIP code mean?
The first digit is the national area (0-9, west to east roughly). Digits 2-3 identify the sectional center facility. Digits 4-5 identify the local post office. The optional 4-digit suffix narrows to a delivery route.
How is ZIP+4 different from a standard ZIP?
ZIP+4 appends a hyphen and four digits to a standard 5-digit ZIP. The extra digits identify a specific city block, building, or delivery route, enabling more precise automated mail sorting.
Does this tool store the ZIP codes I enter?
No. Validation runs entirely in your browser. Nothing is transmitted.