Ensure Your Bar Code Can Be Scanned


There are many things that can go wrong in the production of a bar code after allocating the bar coded number and designing of the artwork. All of these can affect the scanning rate.

Some of the factors that can affect the scanning would be:

  • Print Contrast

  • The print contrast verifies if there is sufficient contrast between the dark bars and light spaces. Sufficient contrast is essential for a good scan.

  • Size and Height of Bars

  • The bar code should be at least the minimum size that is recommended and the height of the bars should not be shorten or truncated.
  • Light Margin Area

  • Light margin area is the width of the space before and after the bar code. There should not be any writing or design too close to the bar code as the scanner will detect it as part of the bar code and will not be able to "recognise" where the bar code starts and stops.

  • Check Digit Calculation

  • Check Digit calculation serves as an accuracy check for the reading of entire symbol by the scanner.
  • Location of the Bar Code on the Packaging

  • Bar code symbols should be placed away from edges of packaging and on a flat surface. Recommendations on the preferred location of the bar code on the products have been drawn up. These guidelines are use to ease and quicken the checkout process. With some form of standardization of bar code location on the packaging, the cashier need not search all over the product for the bar code.


  • How Verification Differs from Scanning

Verification is the technical process by which a bar code symbol is measured to determine its conformance with the specification for that symbol. It tests the scan rate, bar codes specifications following the GS1 International general specifications and quality of the printed bar code. The only reliable way to predict how well a bar code will scan is to test the quality and the technical correctness of the bar code itself.


Scanners alone are not reliable as indicators on how well a bar code will scan because there are several types of scanners for example wands, lasers and cameras. Not only are there are different types of scanners but also different ages and conditions or environment where a bar code may be scanned. The ambient light of a type of reader will vary from others as will the distance of the scanning. A bar code that scans using a wand reader may not be able to be scanned with a laser based scanner. Therefore a verifier is used to verify the specifications and quality of a bar code.


It is recommended that sample in its final packaging is submitted for verification. This gives a more accurate result as factors such as shrink wrap, blister pack, creases or seams will be taken into consideration during the analysis.

 Map to GS1 (Click to zoom)


All Rights Reserved |GS1 (TZ) NATIONAL LTD – Dar Es Salaam P.O. box 2476, Dar es salaam - Tanzania, Tel: +255 22 2150118, Fax: +255 22 2151016
Email:, Website: I Contact Webmaster