The Real Data Lives on the Back
Almost everyone studies the front of a license. The part a machine actually reads sits on the back, inside the dense rectangular block of stacked bars known as a PDF417 barcode. When a doorman runs a card through a reader, that block is what gets decoded, and what comes back is a tidy list of fields that is supposed to match the printed front exactly. This barcode is also what replaced the older magnetic stripe on most cards, a shift covered in the magnetic stripe on ID cards explained.
This guide explains what that barcode stores, how the data is organized under the national standard, and why a card whose back does not agree with its front is the easiest kind to flag. For the human-readable counterpart on the front, it pairs naturally with how to read a license number by state.
One Standard Behind Every State
The layout is not invented per state. The American Association of Motor Vehicle Administrators publishes the DL/ID Card Design Standard that tells every jurisdiction how to pack the barcode, which is why a reader built in one state can parse a card from another. You can see the standard itself on the AAMVA card design standard page.
The barcode opens with a short header: a compliance marker, the issuer identification number that names the state, and the version of the standard in use. After that header comes the data, one field at a time.
The Fields a Scanner Pulls
Each field is tagged with a three-letter element code, then its value. A typical card carries:
- DCS and DAC: the last name and first name.
- DAQ: the license number itself, the same string explained in the front-side number guide.
- DBB and DBA: the date of birth and the expiration date.
- DBD: the issue date.
- DAG through DAK: the street address, city, state, and postal code.
- DAU, DAY, DBC: height, eye color, and sex.
- DCF: the document discriminator, the per-card serial that ties this exact printing to the state record.
That discriminator is worth its own attention, because it is the field people most often get wrong; the detail sits in what the document discriminator is.
Why the Back Must Match the Front
A scanner does not judge whether a name is real. It reports what the barcode says and lets a person compare that against the printed front and the face in front of them. The failure mode that catches weak cards is a mismatch: a birthdate that reads one way in ink and another way in the barcode, or an expiration that does not line up. When the two halves of the card disagree, the reader has effectively done the doorman's homework.
This is why the encoding matters as much as the printing. A card that looks flawless but carries a lazy or generic barcode fails the quiet half of the check. The standard a good card is measured against is the same one in how a fake compares to a real ID.
What the Barcode Does Not Contain
It helps to know the limits too. The PDF417 block holds the cardholder fields above and little else. It does not carry a photograph, it does not phone home to a database, and on its own it does not tell a venue your history. Some readers cross-check the decoded fields against an age, but the barcode itself is just a printed record. For what a scan does and does not do at the door, see how a card passes a scanner.
Why This Matters When You Order
Everything you supply on an order ends up in two places at once: the printed front and the encoded back. If your details are consistent and correctly formatted, both halves agree and a routine scan returns a clean, boring result. That consistency is the whole game, and it starts with getting the order right the first time.
Frequently Asked Questions
What kind of barcode is on a driver's license?
It is a PDF417, a stacked two-dimensional barcode printed on the back. It holds the cardholder data as text, and it is the part most venue scanners actually read rather than the magnetic stripe.
What information does the barcode store?
The printed cardholder fields: name, date of birth, address, license number, issue and expiration dates, height, eye color, sex, and the document discriminator. Each value is tagged with a three-letter AAMVA element code.
Does the barcode hold my photo or a database link?
No. The block stores only text fields and a short header naming the issuing state. There is no image inside it, and the barcode by itself does not connect to any outside record.
Why do scanners flag a mismatched card?
Because the reader compares the decoded barcode against the printed front and the person holding it. If the birthdate or expiration in the barcode does not match the ink, the disagreement is an immediate red flag.
Is the barcode the same in every state?
The structure is, because every state follows the AAMVA design standard. The header names the issuing state, but the field codes and layout are shared, which is how one reader parses cards from anywhere.
What is the document discriminator in the barcode?
It is the DCF field, a per-card serial that identifies one specific printing of a license. Replacing or reissuing a card changes it, so it is one of the fields that has to be internally consistent.