Print at 100%
In the print dialog choose “Actual size” or “100%”, never “Fit to page” or “Shrink oversized pages”. Scaling changes the module width, and a few percent smaller can take a UPC below its minimum. After printing, measure the code with a ruler and compare it with the size the generator showed.
Match the module to printer dots
A printer makes bars from whole dots. When the module is not a whole number of dots, some bars come out one dot wider than others and the code's bar widths drift. The PNG export rounds the module to whole pixels at the dpi you choose and shows the actual module width.
| Printer | Dot size | Good module widths |
|---|---|---|
| Thermal 203 dpi | 0.125 mm | 0.250, 0.375, 0.500 mm |
| Thermal / laser 300 dpi | 0.085 mm | 0.254, 0.339, 0.423 mm |
| Laser 600 dpi | 0.042 mm | 0.254, 0.296, 0.339 mm |
Use vector files where you can
SVG and PDF downloads are vectors: design programs and printers draw the bars at full printer resolution. Use PNG only where a program needs an image, and choose the printer's own dpi (or a multiple of it) so the image is not resampled.
Inkjet and colour
Ink spreads on uncoated paper and makes bars thicker. Print a test on the real label stock. Black bars on white work best; dark blue or green on white usually scans, red bars do not (scanners use red light), and light bars on a dark background fail on most retail scanners.
Test before the whole run
Scan the test print with the scanner that will read it in practice, not only a phone app. For retail products, a barcode verifier gives an ISO grade; many retailers expect grade C (1.5) or better.
Questions
- Why is my PNG barcode blurry?
- The image was scaled after export. Insert it at its own size (the PNG carries its dpi) or use the SVG or PDF instead.
- Which dpi should I choose for a Zebra or Rollo label printer?
- The printer's own resolution: usually 203 dpi, some models 300 dpi. It is on the printer's label or in its settings.