EAN13 and UPC format barcodes
Here is a response to a recent customer enquiry.
There is no doubt that the barcodes we supply are in EAN-13 format, although they can sometimes scan as UPC barcodes. This is because the bars are the same regardless of whether or not it is a UPC-A or an EAN-13 beginning with ‘0’ – as can be seen here Barcode Formats – UPC & EAN13.
The reasons that the bars are the same are a little complicated, but I will do my best to explain below:
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).
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 sides 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, the 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’. – please see attached the EAN-13 parities for a more visual version of this.
The differences between our EAN-13 barcodes and UPC barcodes are the distribution of the digits below the barcode and the fact that it has 13 digits.
However, since the bars are the same, when scanned, many systems will return it as a UPC Barcode as this is the only part of the barcode that a scanner reads.