Because EAN-13 barcodes are more common, people generally prefer to use these as the majority of stores prefer this format. In some cases however a store may prefer of require a UPC-A format barcode for a product that already has an EAN-13 printed on it. This simply means instructing the retailer to ignore the leading ‘0’ on the EAN-13, in which case it essentially turns into a UPC-A barcode. This is because the barcode of the UPC-A without the leading ‘0’ are identical to the bars of the EAN-13 with the leading ‘0’ meaning that they both scan in exactly the same way.
Please see the below image for an example of how this works:
Why this occurs?
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 so they can be scanned upside down and still return the correct number the right way around.
Originally the 12 digit UPC system was created in the 1970’s by George Laurer. – these work with 2 different parities – a left side odd parity and a right side even 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 an additional 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 of the initial 6 digits will use the left odd parity, meaning that the bars look the same as a UPC barcode would 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 times 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, hence, assumes that it is UPC format. When the number is first added to the system in the 13 digit format and linked to the product in the system (this is generally how stores add the barcodes based on the information provided on their buyer form), it tends to scan appropriately as an 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 in the Musgraves in Ireland, they prefer that you fill out your barcode in it’s 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.