PostNet
Courier & ShippingAlso known as: USPS PostNet
Ethan Carter
QR & Barcode Standards Specialist
PostNet is a legacy United States Postal Service barcode that encoded ZIP+4 codes to speed mail sorting.
How it works
Instead of varying widths it uses tall and short bars (height modulation) to represent digits, plus a correction digit.
Where it's used
Historic US mail routing, now largely superseded by the Intelligent Mail barcode.