UPC (Universal Product Code) and EAN (originally European Article Number) are barcode numbers from the GS1 system, which identifies trade items worldwide through the Global Trade Item Number, or GTIN. A UPC-A barcode carries a 12-digit GTIN-12, while an EAN-13 barcode carries a 13-digit GTIN-13; a GTIN-12 can be written as a GTIN-13 by adding a leading zero. The final digit is a check digit, and the first part is a company prefix allocated by a GS1 member organisation.
In music, the barcode identifies the product, meaning a release as a whole: a single, an EP, an album or a particular edition. The individual tracks on it are identified separately by their ISRCs. Digital distributors ask for a UPC or EAN for every release and often provide one when the label does not have its own GS1 prefix.
A changed product, such as a deluxe edition with bonus tracks, normally needs a new barcode, while the recordings it contains keep their existing ISRCs.