When you create new product pages and offer listings, products must be associated with industry-standard IDs for most categories. Product IDs let Amazon match identical products, avoid duplicate listings, and help customers easily find and compare offers. You can check category requirements here.
Product IDs are part of a system of unique identifiers called Global Trade Item Numbers (GTINs). The most common GTINs for creating Amazon catalog pages are UPCs, ISBNs, EANs, and JANs.
Some products don't have a GTIN. If the product is already listed on Amazon, you can list your offer
on the existing product detail page without providing a GTIN. If the product isn't listed yet, you can apply for a GTIN exemption
for your category (if eligible). Brand owners and manufacturers can also enroll their brands
in Amazon Brand Registry to protect their registered trademarks and get a product ID.