PDF417 barcode

The dense barcode on the back of most US and Canadian driver's licenses.

It looks like a tall block of thin black stripes and holds the same details that are printed on the front, in a form a scanner can read.

A two-dimensional barcode format that the American Association of Motor Vehicle Administrators (AAMVA) standard specifies for driver's licenses in the US and Canada, encoding the holder's demographic details and the license's issuance data. The name PDF417 comes from Portable Data File, with 417 describing how each character is built from bars and spaces.

A barcode check typically works like this:

1. The system captures an image of the back of the license.
2. It decodes the barcode into its data fields.
3. It compares the decoded data with the text printed on the front.
4. A mismatch is a sign of tampering or a fake.

The decoded data is useful in several ways:

• Fast capture, since a scan fills in fields without relying on text recognition.
• Consistency checks, since the barcode and the printed text should agree.
• Record checks, since the decoded details can be sent to the issuing agency's records for confirmation.

The PDF417 barcode sits next to terms that are easy to mix up:

• Machine-readable zone is the text-based equivalent on passports and ID cards.
• Document tampering is the alteration of a real document, which a barcode mismatch can reveal.
• Government source-of-truth validation can check the decoded details against the issuer's records.