PDF417 barcode vs magnetic stripe — what each checks
Great question. The scanner reads the PDF417 barcode first, so if that's dead or throws a data parsing error, the mag stripe won't matter. Proper AAMVA compliance is key—most checks I've seen go by the barcode format. The mag stripe usually mirrors it for backup but doesn't have the same data structure. Keep the barcode healthy or you'll get flagged, even if the stripe scans fine.
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These two elements on a driver's license serve different functions and are checked in different contexts. Understanding which one a venue is reading changes how you interpret a scan success or failure.
The PDF417 barcode
The 2D barcode on the back of a US driver's license encodes a structured data payload defined by the AAMVA standard. It contains the full name, address, license number, date of birth, expiration date, physical description fields, and various issuing jurisdiction codes. This data is encoded digitally and verified by decoding the barcode — it is not looked up against an external database in most venue scanners.
When a venue scanner reads the barcode, it decodes this payload and either displays it on screen for a human to verify against the card face, or checks it against basic validity rules (expiration date in the future, age above a threshold). Local decode is fast and works offline.
The magnetic stripe
The magnetic stripe uses a different format — AAMVA-standard three-track encoding — but contains a subset of the same information. It is read by swiping the card through a reader rather than scanning it optically. Magnetic stripe readers are more common in retail and liquor store environments than in bar and club settings.
The stripe data is plain ASCII with no encryption. Any data on the stripe can be read with a basic mag stripe reader and needs to be consistent with the printed card face information to pass a check that compares both sources.
Which is more commonly checked
In bars and clubs, the PDF417 barcode is read far more often than the mag stripe. In age-restricted retail, both are common. Some states have moved to only the barcode on newer card generations. If a venue scanner checks the mag stripe and the barcode data does not match, that discrepancy is a problem. Consistent encoding across both elements is what quality vendors produce.