USPS Intelligent Mail Barcode API

The Intelligent Mail Barcode is the USPS height-modulated barcode that encodes a 20 to 31 digit routing and tracking code across four bar states: ascender, descender, tracker, and full bar. Introduced in 2009 and made mandatory for USPS automation pricing in 2013, it replaced the earlier POSTNET and PLANET codes with a single symbol that carries both delivery point routing and unique mailpiece tracking data for USPS Confirm services.

BarGen renders an Intelligent Mail Barcode from a 20 to 31 digit numeric string through the REST API, returning SVG or PNG output formatted to USPS bar height and spacing specifications.

The Intelligent Mail Barcode (IMB), also known as the 4-State Customer Barcode, is a 65-bar code used by the United States Postal Service (USPS) for mail routing and tracking. It replaced POSTNET and PLANET barcodes in 2013.

The barcode encodes 31 digits of data: a 20-digit tracking code (barcode ID, service type, mailer ID, and serial number) and an optional 0, 5, 9, or 11-digit routing code (ZIP code information). This enables both tracking and delivery point routing.

IMB uses four bar states: full bar, ascender (top half), descender (bottom half), and tracker (middle third). This 4-state encoding allows high data density while maintaining readability by high-speed mail sorting machines.

Using IMB qualifies mailers for postal discounts and provides full visibility into mail delivery. The USPS Informed Visibility service uses IMB data to provide real-time tracking of mail pieces through the postal network.