Barcode Scanning Tips

Colors, contrast and printing choices that make barcodes scan.

Most retail and warehouse scanners light the barcode with red light, around 630 to 670 nm, and measure how much is reflected. Under red light, red, orange, pink and yellow look as light as white, so bars in those colors seem to vanish, while the same colors work as a background. Dark bars on a light background are the rule: black on white is best, and dark blue, dark green or dark brown bars on white, cream or light yellow work too.

Contrast is only part of it. Barcodes also fail because they're printed too small, cut too short, crowded by text in the quiet zones, wrapped around a tight curve with the bars running the wrong way, or printed on glossy or see-through material. The tables below cover colour choices and the faults print and packaging teams see most, with the fix for each.

Bar and background colors

For red-light laser and LED scanners. Camera-based imagers are more forgiving but need contrast too.

Bars	Background	Scans?	Why
Black	White	Yes, best	Maximum contrast under any light
Dark blue, dark green or dark brown	White or light	Yes	Dark under red light
Black	Yellow, orange or light red	Usually	Warm backgrounds reflect red light like white
Red, orange, pink or yellow	White	No	Red-light scanners see the bars as white
White (reversed)	Black or dark	Often not	Many scanners and standards expect dark bars; avoid for retail
Black	Dark blue, green or brown	No	Not enough contrast
Gold, silver or metallic ink	Any	Unreliable	Shiny ink reflects unpredictably
Dark bars	Clear film or foil	Unreliable	Print a white box behind the barcode

Common faults and fixes

Problem	What happens	Fix
Barcode printed too small	Bars blur together, especially on rough paper	Stay at 80% magnification or more for EAN/UPC; bigger on cartons
Bars cut short (truncated)	Scanners must hit it straight on	Keep the full nominal height
Text or edges in the quiet zone	The scanner can't find the start or end	Keep the margins clear: 11X/7X for EAN-13, 9X for UPC-A
Bars around a tight curve	Ends of the barcode bend out of view	On small cans and bottles, turn the barcode 90° so the bars are horizontal and it runs along the straight side (ladder orientation)
Ink spread (bar gain)	Bars grow and spaces shrink	Ask the printer for bar width reduction or print larger
Glossy or laminated label	Glare hides the bars	Use matte material or angle the scanner
Barcode on a fold, seam or edge	Part of the bars is hidden or distorted	Place it on a flat panel away from edges
Low-toner or draft printing	Grey, broken bars	Print in normal or best quality and replace toner

Good to know

Test before you print thousands

Print a sample on the real material and scan it with the kind of scanner it will meet. A barcode verifier grades print quality from A to F to ISO/IEC 15416 (1D) or 15415 (2D), and some retailers ask for a minimum grade; a phone scan only shows that it reads.

Design barcodes

Decorative barcodes keep the same rules: the plain part of the bars needs full contrast and the quiet zones stay clear. Keep at least about 60% of the bar height plain.