Packaging · 4 min read
Barcodes and QR codes that actually scan
A barcode is the one element on a pack that has a pass or fail test applied to it by a machine, in a shop, in front of a customer. Everything else on the carton is a matter of taste. This is not, and the failures are almost always introduced at design stage by someone treating the code as a graphic.
Size is not a design decision
Retail barcodes have a defined nominal size and a permitted range around it. Scaled below that range the bars become too fine for the scanner to resolve reliably, particularly once print gain on absorbent board thickens them slightly.
Designers shrink barcodes because they are ugly and space is tight. It is the most common cause of a code that scans in the studio and fails at the till, because a desktop scanner reading a laser print is a far more forgiving test than a supermarket scanner reading a printed carton.
The quiet zone is part of the code
A barcode needs clear space either side, with nothing printed in it. That margin is how the scanner finds where the code begins and ends, so it is functional rather than cosmetic white space.
Anything intruding, a rule, a logo, a fold, an adjacent block of text, can stop the code reading entirely. When space is tight this is the first thing to get eaten, and it should be the last.
Contrast, and the colours that fail
Scanners read contrast, and most read in the red part of the spectrum. Black bars on white is the reliable combination and there is no good reason to depart from it on a retail pack.
The failures are predictable: red bars, which many scanners simply cannot see; light bars on a dark background, which inverts what the scanner expects; and metallic or reflective substrates, which scatter the beam. If the brand demands a coloured code, it must be tested on the real substrate, not approved on screen.
The substrate changes the result
The same artwork behaves differently on different materials. Uncoated board absorbs ink and spreads the bars. Gloss lamination and varnish add reflection. A code printed across a fold or a crease distorts as the carton is erected. A code on a flexible pouch moves and curves.
Good printers compensate by adjusting bar width for the expected gain on the chosen substrate. This is a pre-press decision, which is another reason to send the printer the barcode as artwork to place rather than a picture of one embedded in the design.
QR codes have their own rules
QR codes are more tolerant, but not unconditionally. They need a quiet zone too, they need contrast, and they need enough physical size for the scanning distance: a code read from across a room must be far larger than one read from the hand.
The bigger QR risk is not printing at all, it is what the code points to. A printed code is permanent and the URL behind it is not. Point it at a stable address you control rather than a campaign link, or the pack outlives the page and sends customers to a dead end for the rest of its shelf life.
Test before the run, not after
Get a printed sample on the real substrate with the real finish, and scan it with more than one device, including a proper scanner rather than only a phone. If it needs several attempts or a particular angle, it will fail in a shop.
We place and verify codes in pre-press as part of the carton work in Lahore, adjusting for gain on the specified board. Send the code as supplied data rather than as part of the artwork, and it can be built correctly rather than reproduced faithfully at the wrong size.
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