What is a UPC?
The Universal Product Code is the product number used in retail in the United States and Canada. UPC-A has twelve digits: a number system digit, a company prefix, an item reference and a check digit. The same number is also a GTIN-12, and writing it with a leading zero turns it into an EAN-13 - one identifier, three names.
UPC-A and UPC-E
UPC-E is not a separate numbering system. It is a UPC-A that contains a run of zeros, written without them, so that the symbol fits on a lipstick or a pack of chewing gum. A scanner expands it back to the full twelve digits before the till sees it, and the number system digit of a UPC-E can only be 0 or 1.
How the check digit works
The last digit is a modulo 10 check digit over all the digits before it: counted from the right, they are weighted alternately three and one, added up, and the check digit is whatever completes that sum to the next multiple of ten. It catches most single digit typos and most swapped neighbours, which is all a check digit is meant to do.
What the numbers on this page are
They are test data. Every code here is structurally valid and unlicensed: it can populate a database, a scanner test or a classroom exercise, and it identifies no product anywhere.
Why a random UPC will fail on Amazon
A generated code is structurally right - the length fits and the check digit matches. It is not licensed. Every real UPC begins with a GS1 company prefix that GS1 issued to one named company, and that assignment is what a marketplace looks up. Amazon validates product identifiers on new listings against the GS1 registry, so a number that was never issued, or one that belongs to somebody else, is refused at listing time or removed later. eBay, Walmart and Google Shopping apply comparable checks to the identifiers in a listing or a product feed.
How a GTIN exemption works
Marketplaces do have a route for products that genuinely carry no barcode: handmade goods, private label items, spare parts, bundles. Amazon calls it a GTIN exemption and grants it per brand and product category, after which the product can be listed without an identifier. eBay accepts a Does not apply value in the identifier field for the same kind of item. The exemption is the honest answer to not having a barcode. A generated number is not.
What GS1 licensing actually costs
GS1 is a not-for-profit organisation with a separate member organisation in each country, and every one of them publishes its own price list. The shape is usually the same: a one-off joining fee plus an annual licence fee, scaled by how many codes you need and in some countries by company turnover. Because the amounts differ per country and are revised over time, read the figure off the price list of the GS1 organisation in your own country rather than off a third party page.