Matrix symbology
PDF417
PDF417 is a stacked linear symbology that holds far more data than a one-dimensional barcode while still being read by a scanning laser rather than requiring a camera. It is wide and short by nature, and it is what sits on the back of driving licences and boarding passes.
Specification
These are the values the editor enforces while you design, not figures collected from elsewhere — the same numbers its quiet-zone and resolution checks run on.
| Property | Value | In context |
|---|---|---|
| Minimum X-dimension | 0.254 mm | 0.0100 in · 10 thou |
| Quiet zone | 2 modules | 0.51 mm at the minimum X-dimension |
| Dimensionality | Matrix (2D) | Requires an imager or camera |
PDF417 at 203, 300 and 600 dpi
A printer can only place whole dots, and 0.254 mm is not a whole number of them at any of these resolutions. What changes is how much a single dot of rounding costs you as a share of the narrow bar.
| Resolution | Narrow bar in dots | Printed as | Rounding error |
|---|---|---|---|
| 203 dpi | 2.03 | 2 dots | 1% |
| 300 dpi | 3.00 | 3 dots | 0% |
| 600 dpi | 6.00 | 6 dots | 0% |
What PDF417 encodes
Text, numbers and binary data at high capacity, arranged in stacked rows. Selectable error-correction levels trade capacity against damage tolerance, and the symbol's aspect ratio can be tuned by changing how many columns it uses.
Where it is used
- Identity documents including driving licences
- Boarding passes and transport tickets
- Shipping labels carrying a full address block in the symbol itself
Check digit
None. PDF417 uses Reed-Solomon error correction at a level you choose, which both detects and repairs damage rather than simply flagging it.
How PDF417 fails in practice
- Fitting it into a square space. PDF417 is inherently wide, and forcing a square aspect ratio drives the row count up and the symbol's readability down.
- Choosing a low error-correction level for a document that will be handled repeatedly, where wear is expected rather than exceptional.
- Assuming a phone will read it as easily as a QR code. Support exists but is less consistent than for QR.
When to use something else
- QR Code — choose it instead when the reader is a phone camera and the shape can be square.
- Data Matrix — choose it instead when the data will fit and the smallest possible footprint matters most.
Questions about PDF417
- Why is my PDF417 so wide?
- It stacks rows of a linear code, so it is wide by construction. You can trade width for height by reducing the column count, but a PDF417 will never be as compact as a true matrix symbology like Data Matrix.