Barcodes are a visual technology. A simple way to test a barcode is to look at it—it just makes sense. Here’s what to look for:

• Linear barcodes (parallel lines and spaces) always have bars of various widths. Look for the narrow bar and compare its width to the narrow space. They should be the same.
• 2D barcodes (Data Matrix and QR Code) use dots or squares of the same size, clustered together to form patterns. Look for an isolated dark square, and compare it to an isolated light square. They should be the same size.

If your barcodes fail this simple test visual test, chances are the dark bars or squares are larger than their light space equivalents. You have print gain. If the difference is relatively small, it may not cause a scanning problem, but if the light spaces are significantly smaller, scanning will be impacted.

Here is another visual test.

Are there graphics, images, border lines, or corners close to the barcode? Linear barcodes must have blank spaces of about ¼” flanking the left and right sides. 2D barcodes need a blank space of about 1/8” on all four sides. Anything encroaching these areas will defeat the barcode.

A third factor is color. Barcodes don’t scan if they are printed in a red or reddish color or if the background is green. That’s because the scanner uses red light. Black barcodes on a white background work best. Another factor is color uniformity. The barcode image must be uniformly dark, and the background must be uniformly light. The key issue is uniformity. Variations such as a gradient, an image, or a pattern might look great, but they kill the barcode.

How not to test a barcode?

Using a scanner to test a barcode is useless. It only tells you whether the barcode works or doesn’t. It doesn’t tell you if it’s close to not working. If a barcode fails to scan, the scanner doesn’t tell you why and how to improve it.

Using a smartphone is even worse. The scanner uses red light, while a smartphone uses a white flash or ambient light. It will scan barcodes that a scanner can’t and make you believe it’s okay. That could be an expensive problem.

Your visual examination of a barcode can detect two of the most common barcode problems, but the best way to test a barcode is with a verifier. If you’d rather not buy one, use a testing service.

For more information about barcode testing, contact us. It’s what we do.