The diagram at left shows the relationship of an individual codeword to a PDF417 barcode as a whole. The diagram at right shows a single codeword broken down into its 4 bars and 4 spaces, as well as its 17 units of width — the reason behind the “417” in the name. It is possible to make 929 unique codewords using this pattern, each of which can represent numerals, letters, or other data.
For check scanners, PDF417 is important because it is the standard barcode format for most state-issued driver’s licenses and ID cards, including all that are issued in compliance with the federal Real ID Act. Many banks and credit unions have begun using check scanners to capture images of customer IDs at the teller window, making the ability to identify and read PDF417 format a key capability for data extraction and validation.