PDF417

Stacked, not matrix

PDF417 predates QR by three years: invented in 1991 by Ynjiun Wang at Symbol Technologies, later ISO/IEC 15438. The name decodes its own geometry: Portable Data File, with each codeword drawn as 4 bars and 4 spaces across 17 units. Symbols are 3 to 90 stacked rows flanked by start/stop bar patterns, which is why a PDF417 looks like a dense 1D barcode that grew downward rather than a square mosaic. Being row-structured, it can be read by sweeping laser scanners as well as cameras, a genuine advantage in 1991, mostly irrelevant now that 2D imagers are universal.

Capacity peaks around 2,710 digits, 1,850 text characters or 1,108 bytes, with selectable Reed–Solomon security levels.

Where you meet it

The back of every US and Canadian driver's licence carries a PDF417 encoding the AAMVA data elements (name, date of birth, licence number), which is what bars and car-rental desks scan. Printed (not mobile) boarding passes, shipping labels and some visa documents use it too.

For anything new, its economics are poor: PDF417 typically needs 3–4 times the area of a QR code for the same payload, and phone camera apps rarely read it. It persists where regulation froze it in place. See QR vs PDF417 for the comparison, and reach for a QR generator otherwise.

FAQ

What is the barcode on the back of a driver's licence?

A PDF417 symbol. In the US and Canada it encodes the AAMVA standard's data elements: the same information printed on the front, in machine-readable form.

Is PDF417 better than a QR code?

Rarely. It needs several times more area for the same data and phone cameras seldom read it. Its remaining strengths are legacy laser-scanner compatibility and mandated uses like licences.

What does the 417 in PDF417 mean?

Each codeword is drawn as 4 bars and 4 spaces spanning 17 module widths, 4-1-7.