Barcode Format

We normally supply EAN-13 barcodes with a leading ‘0,’ i.e. in the format 0213456789104. In some places, however (mostly the USA), they prefer UPC-A 12 digit barcodes. This is fine in the case of our numbers, as the actual barcodes of the EAN-13 barcode are identical to those of a UPC-A barcode if the leading ‘0’ is ignored. This means that if a store requires a UPC-A barcode instead of an EAN-13, they can be instructed to ignore the leading ‘0’ when entering the barcode into their system. Please see the image below for an example of how this works.



Why does this occur?

The way a digit is encoded into every barcode is 7 blocks of either white or black, making up each digit. A full set of digits 0-9 is called a parity. Retail barcodes have a minimum of 2 parities, one for the left side and one for the right. This is to be scanned upside down and still return the correct number the right way around.

Originally the 12 digit UPC system was created in the 1970s by George Laurer. These work with 2 different parities – a left side odd parity and a right-side parity (each with 6 digits). The parities for these can be seen in the attached.

Later, a 13 digit EAN-13 system was introduced as a superset of the UPC barcodes. These were deliberately designed to be used in conjunction with UPC-A barcodes. And hence, employed both the left odd parity and the right even parity of the UPC barcodes, but added parity (a left-even parity) which was to be used on a selection of the left-hand side digits –

The left and right-hand side of the EAN-13 barcodes are still divided into 6 digits each. So the initial digit determines which combination of the first 6 digits will use the newly created left even parity. Hence, in no EAN-13 barcode is the first digit encoded in the barcode. However, it does determine the way the other digits are encoded.

In the case of a leading ‘0’ as with our barcodes, the 0 determines that all initial 6 digits will use the left odd parity. This means that the bars look the same as a UPC barcode without the leading ‘0’ – As the UPC version also only uses the odd parity.

How do they scan?

Because the actual bars are the only part of the barcode that is scanned (i.e. the scanner isn’t reading the digits below the barcode), an EAN-13 barcode with a ‘0’ on the front can sometimes be confused by scanners as a UPC barcode without the ‘0’ and vice-versa. This is largely to do with what the scanner or software system is expecting to see. Often, this occurs when a barcode that is not linked on the system is scanned – The software has no point of reference for what format the barcode should be and assumes that it is UPC format. When the number is first added to the system in the 13 digit format and linked to the system in the system (generally how stores add the barcodes based on the information provided on their buyer form), it tends to scan appropriately EAN-13 format barcode.

Very few stores have had issues with this in the past. And when issues occur, they are generally resolved easily. If you are going to the Musgraves in Ireland, they prefer to fill out your barcode in its UPC format on their buyer form (without the leading ‘0’) and state that the format is UPC. If this is done, they have no problems using our barcodes.

Please contact us if you have any questions about this.


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