Printing guidelines for QR codes and barcodes
Best practices to ensure that your printed codes are easily scanned.
When these codes are printed, it's crucial that each element is legible for a smartphone or scanner. The texture of your material, the print process, and the ink color, and the size of your code can all affect the clarity of the printed code, and in turn the scannability.
There are several best practices to ensure that your printed code is scannable, but keep in mind that the best way to ensure a printed code is scannable is to pull out your phone and test it.
The texture of your material is one factor that can affect scannability. The more textured and uneven your surface, the more likelihood that ink could spread, blurring the lines between elements. For better scannability, your code should be larger on more textured surfaces.
In general, paper surfaces are more textured than plastic. For example, the paper fibers of a box create a more textured printing surface than the melted polymers of a poly mailer.
- Plastic is generally smoothest.
- Paper is more textured than plastic. The higher the percentage of recycled content, the more texture a paper will have. This is because recycled fibers are shorter than virgin fibers and these shorter fibers give the paper more texture.
- Corrugated boxes are more textured than flat paper due to their wavy surface. Typically, the smaller the flute size of your corrugated board, the smoother the print surface will be because there is less distance between each flute and the paper can lay more flat.
Beware of printing on glossy surfaces. The shine creates a glare that can prevent easy scanning.
A rule of thumb for the size of a QR code is
Scanning Distance ÷ 10. So if your code is scanned from 10 inches away, it should be 1 inch across. This is a great starting point, but are a more consistent print metric to consider is line weight.
While the size of the code is important, it's also crucial on consider the amount of white space around the code and between its modules. A module (aka X-dimension) is the smallest unit in a scannable code. In a QR code, a module is an individual square. In a barcode, a module the thinnest bar.
- Minimum module width: For printing, we advise that the smallest module in your code be no thinner than 1.5 pt (0.52 mm) across.
- Padding: Padding (aka a quiet zone) around your code gives the scanner space to recognize it. For QR codes, padding should be at least the width of the 4 modules; for barcodes, it should be at least the width of 9 modules. Consider adding more space if a 1/8" plate shift could put your QR code in a danger zone (on a fold line, close to a cut line, etc)
Error correction: QR codes can vary in complexity depending on the amount of redundancy (aka error correction) and the length of the url. Error correction repeats module groupings to increase the likelihood of scannability even if your code gets damaged.
With a QR code generator, you can choose a level of error correction: Low, Medium, Quartile, or High. The higher the error correction, the more modules will populate your QR code, so you'll likely have to size up to meet the minimum module width.
Each print process has different capabilities and ink traits which can affect the precision and clarity of an image.
If you're using a less precise print process (like flexographic printing), you should consider scaling up your code to increase the minimum module width (1.5 pt) to account for any ink bleed that could fill the gaps between the modules and affect scannability.
Lithographic and rotogravure printing are generally more precise due to the material of the print plate.
Colors to avoid
Some QR code scanners can't read light colored codes printed on dark backgrounds — this includes light ink on natural kraft. To be safe, we advise printing your code in a darker color on top of a light colored ink or material.
If you're printing a barcode, avoid using red to print the code itself because laser scanners read red as white.
Your code should be as high contrast as possible so that it's easily distinguished from the background. Your contrast ratio should be at least 4:1. You can use this tool to find the contrast ratio of your colors.
Tip: If your packaging design uses just one color of ink, adding a second color for your barcode or QR code adds the cost of a second print plate.
To avoid a second print plate and keep your code dark-on-light, consider removing a square of your ink color and printing your code inside of the empty square, using your one ink color.
If you want to err on the side of caution, bigger codes are better, and avoid printing in light colors.
If you have any doubts about the scannability of the final print, your best bet is to test it. If you have time to get a printed prototype before your full run is produced, that is ideal.
- Keep your QR code square: Warping or stretching the QR code will make it unscannable
- Keep all the modules of your code "grouped" in your design program so that no stragglers are left behind.
- Save your QR code as a .svg, .pdf, or .eps to preserve the integrity of the code and avoid pixelation or blurriness in scaling.
- If your code is customer facing, add a call-to-action to encourage them to scan.
When you download a Lumi ID QR code, it's already saved in the svg format.