GS1-12 Symbology Information

GS1-12 barcodes formerly know as UPCa are used mainly in the USA for retail product labelling.

They are 12 digits long, the last digit being a check digit calculated from the other digits.

They have a hidden first digit of 0 that is used when calculating the check digit.

There is also an optional 2 or 5 digit extension which can be used to encode additional information but is not usually used for standard products.

These barcode numbers are allocated by GS1, a global organisation that allocates a company prefix to members for a yearly fee. You can apply for a company prefix for your products when you become a member.

This is why no two products in the world have the same barcode in a retail environment.