EAN13 and UPC format barcodes

Here is a response to a receipnt customer enquiry.

There is no doubt that the barcodes we supply are in EAN-13 format, however you are quite right that they can scan as UPC barcodes as well. 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 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).

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’. – please see attached the EAN-13 parities for a more visual version of this.

The differences between our EAN-13 barcodes and UPC barcodes is both the distribution of the digits below the barcode and the fact that it has 13 digits.

However due to the fact that 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.