ASIN (Amazon Standard Identification Number)

Every Amazon product has an ASIN, the 10-character alphanumeric identifier Amazon uses to track it internally. ASINs appear in product URLs as /dp/B0ABCD1234 or /gp/product/B0ABCD1234. Affiliate links typically include the ASIN plus your tag: amazon.com/dp/B0ABCD1234?tag=you-20. Without the ASIN, an Amazon affiliate URL cannot point at a specific product.

The format. ASINs are 10 characters, alphanumeric, and case-sensitive. Books (added to Amazon before ASINs existed) use the ISBN-10 as their ASIN. Everything else uses a generated identifier that almost always starts with B0. You can copy an ASIN from the product URL or find it explicitly listed in the "Product information" or "Additional information" section near the bottom of any Amazon product page.

ASIN versus SKU, UPC, EAN, and GTIN. Easy to confuse and worth getting right. The SKU (Stock Keeping Unit) is the seller's internal product code; each Amazon seller assigns their own SKUs and they are not visible to buyers. UPC (Universal Product Code) and EAN (European Article Number) are the barcodes printed on packaging, issued by GS1. GTIN (Global Trade Item Number) is the umbrella standard that includes UPC and EAN. The ASIN is unique to Amazon, while UPC, EAN, and GTIN are universal across retailers. One product can map to one ASIN on amazon.com, a different ASIN on amazon.de, the same EAN everywhere, and as many SKUs as there are sellers listing it.

ASINs are locale-bound. The same physical product can have entirely different ASINs across amazon.com, amazon.co.uk, amazon.de, amazon.fr, and amazon.co.jp. This matters for affiliate links because your affiliate tag is also locale-bound. A working amazon.com/dp/B0ABCD1234?tag=you-20 link does not become a working amazon.de link by swapping the domain. You need the German ASIN and a separate amazon.de Associates tag for the same product. SiteStripe only generates links for the locale you are currently logged into.

ASINs are supposed to be permanent. In practice they are not. Amazon reassigns or deactivates ASINs more often than creators expect. Common triggers: a seller pulls inventory, a product line is restructured, a counterfeit listing is taken down, two listings get merged, or Amazon migrates a category. When this happens your old affiliate link still resolves with a 200 OK status, but the page now shows a different product, a stripped-down placeholder, or redirects to the homepage. This is the single most common reason Amazon affiliate links silently break, and Amazon does not notify Associates when it happens.

Detecting ASIN drift. A standard uptime checker will not catch this; the status code stays 200. The reliable signals are the affiliate tag missing from the resolved page, the rendered product title not matching the title you originally linked to, or the URL silently redirecting to /. Affiliate-link monitoring tools detect these by reading the destination page, not just pinging its status code. The category-level fallout from a single ASIN reassignment can be significant for creators whose review content is built around a specific product.