POSTNET Generator

USPS POSTNET barcode encoding ZIP codes for mail sorting, height-modulated bars.

How POSTNET is structured

POSTNET encodes the delivery point in height-modulated bars: each digit is five bars, two tall and three short, and a tall frame bar closes each end of the symbol. The payload is a five-digit ZIP Code, a nine-digit ZIP+4, or an eleven-digit ZIP+4 plus a two-digit delivery point, so the symbol length tells the sorter how precise the address on the mailpiece is.

POSTNET check digit

The last digit is a check digit computed so that all digits in the symbol — payload plus check — add up to a multiple of ten. The rule is the same one PLANET uses, and it catches a single misread bar as an invalid total rather than as a plausible neighbouring address.

POSTNET compared with PLANET

PLANET is the same five-bar symbol carrying a tracking identifier instead of a delivery point, and the Intelligent Mail barcode supersedes both with a 65-bar, four-state symbol that carries tracking and routing together. For current mail, IMb is the symbol that earns automation pricing. Compare the PLANET generator page for the same breakdown of structure, check digit and use cases.

Common POSTNET problems

The check digit was copied rather than computed

POSTNET validates on the multiple-of-ten rule, so a check digit carried over from a different ZIP fails. Enter the payload digits and let the check digit be calculated, then confirm the total is a multiple of ten.

The preview is not a USPS POSTNET symbol

This page renders the digits with the site's Code 128 encoder so the data and label layout can be checked. Mail that has to clear a USPS sorter needs POSTNET output from a mailmarking-capable service.

The address is not DPV-confirmed

A delivery point barcode is only as good as the address behind it. POSTNET requires a standardised, delivery-point-validated address; generating the symbol from an unverified list produces mail that still needs manual handling.

Where POSTNET is used

Not sure this is the right symbology? The barcode format guide groups every supported 1D and 2D format by industry with its character set and limits.