PDF417

PDF417 is a stacked linear barcode format used in a variety of applications such as transport, identification cards, and inventory management.

PDF417 is one of the formats (along with Data Matrix) that can be used to print postage accepted by the United States Postal Service.

PDF417 is the standard selected by the Department of Homeland Security as the machine readable zone technology for RealID compliant driver licenses and state issued identification cards.

PDF417 barcodes are also included on visas and border crossing cards issued by the State of Israel (example).

The clusters allow portions of the symbol to be read using a single scan line that may be skewed from the horizontal.

The three major modes encode different types of data in different ways, and can be mixed as necessary within a single bar code: When the PDF417 symbol is created, from 2 to 512 error detection and correction codewords are added.

When the symbol is scanned, the maximum number of corrections that can be made is equal to the number of codewords added, but the standard recommends that two codewords be held back to ensure reliability of the corrected information.

In order to minimize the effect of these crossings, the PDF417 modules are tall and narrow — the height is typically three times the width.

That area does not count other overhead such as the start, stop, row, format, and ECC information.

Other 2D codes, such as DataMatrix and QR, are decoded with image sensors instead of uncoordinated linear scans.

An 8 bit code word will take 8 square modules (ignoring recognition, alignment, format, and ECC information).