What Is an ASIN on Amazon?
An ASIN (Amazon Standard Identification Number) is the 10-character alphanumeric code Amazon assigns to each product in its catalog; it identifies one detail page that every seller of that exact item shares.
Amazon generates the ASIN when a product is created in the catalog. Most start with B0, and for books the ASIN is the ISBN-10. You can find it in the product details section of a listing and in the page URL after /dp/.
How ASINs work with sellers and variations
Every seller offering the same item lists against the same ASIN, which is why one detail page can carry several offers competing for the Buy Box. Each seller links its own SKU to that ASIN. In a variation family, every size or color is a child ASIN under one non-buyable parent (see parent-child ASIN).
The ASIN is separate from the UPC or GTIN printed on your packaging. Amazon uses the barcode to match or create the catalog entry; the ASIN is Amazon's own identifier.
Why it matters
Ads, reports and tools are organized by ASIN: product targeting, Brand Analytics, Business Reports and nearly every third-party tool. A clean ASIN structure keeps that data readable.
Common mistake
Creating a new ASIN for a product that already exists in the catalog. Amazon's policies prohibit duplicate listings, and a duplicate splits reviews and sales history between two pages.