postnet

POSTNET, short for Postal Numeric Encoding Technique, is a barcode symbology developed by the United States Postal Service (USPS) to automate mail sorting. First introduced in the 1980s, it encodes destination information on mailpieces to improve processing speed and accuracy for automated equipment.

The code uses a single bar height variation, with tall (long) and short bars forming the pattern. Each digit is represented by a five-bar pattern, and the sequence includes start and stop patterns that help scanners read the code in the correct direction. Print quality and contrast are important for reliable optical scanning, and POSTNET barcodes are typically placed in a standardized location on envelopes and packages.

POSTNET supports several data configurations to convey routing information. The basic 5-digit ZIP version encodes the destination ZIP code; extended forms add ZIP+4 data, and there is also a 11-digit Delivery Point Bar Code (DPBC) variant that includes routing to a specific delivery point. Collectively, these options allow USPS processing centers to route mail through multiple sorting stages with greater accuracy.

In practice, POSTNET was widely used to enable automated sorting and tracking of mail before and during initial transitions to newer barcoding systems. In the 2000s and 2010s, USPS introduced the Intelligent Mail Barcode (IMb), which consolidates POSTNET data with additional information for enhanced tracking and measurement. As a result, POSTNET has been gradually phased out for new mailings, though it may still be encountered on older mail or in certain contexts.

See also: United States Postal Service, ZIP Code, Intelligent Mail Barcode, DPBC.