An ASIN, or Amazon Standard Identification Number, is a unique 10-character alphanumeric code that Amazon assigns to every product in its catalog. Think of it as Amazon’s internal SKU system. Every item you see on Amazon, from a phone case to a bestselling novel, has one. If you’ve ever wondered what that string of letters and numbers in an Amazon URL means, it’s most likely the product’s ASIN.
How ASINs Are Structured
Each ASIN is exactly 10 characters long, made up of letters and numbers. Most ASINs for non-book products start with “B0” followed by eight more characters. For books, the ASIN typically begins with a number rather than a letter, and in many cases it matches the book’s ISBN-10 (the 10-digit version of the International Standard Book Number used across the publishing industry).
No two products share the same ASIN. Once Amazon assigns one, that code permanently identifies that specific product listing. If a product is discontinued and the listing is removed, the ASIN doesn’t get recycled for something else.
Where to Find an ASIN
There are two quick ways to locate any product’s ASIN. The fastest is to look at the URL in your browser’s address bar while viewing a product page. The 10-character code embedded in the web address, usually right after “/dp/”, is the ASIN.
You can also scroll down to the “Product Details” or “Product Information” section on any Amazon listing. The ASIN is listed there alongside other details like the manufacturer, item weight, and date first available.
How ASINs Get Assigned
Sellers don’t create ASINs directly. When you list a new product on Amazon, you provide a product identifier called a GTIN, which is usually a UPC barcode number, an EAN (the international equivalent), or an ISBN for books. Amazon then either assigns a brand-new ASIN to your product or matches it to an existing ASIN if that same product is already in the catalog.
This matching system is intentional. Amazon wants all sellers offering the same product to appear under one listing rather than creating duplicates. If you’re selling a product that already exists on Amazon, you list it under the existing ASIN. You only get a new ASIN when your product is genuinely new to the catalog.
How Books Are Handled
Books follow slightly different rules. When a book is published through Amazon’s Kindle Direct Publishing platform, Amazon assigns it an ASIN automatically. Kindle ebooks don’t need an ISBN to be listed on Amazon at all; the ASIN is sufficient for Amazon’s catalog.
Print books are a different story. Most print books on Amazon carry both an ISBN and an ASIN. The ISBN allows the book to be distributed and identified across bookstores, libraries, and other retailers worldwide, while the ASIN handles searchability and cataloging within Amazon’s ecosystem. If you’re a self-published author, your print edition will typically end up with both identifiers.
Parent and Child ASINs
When a product comes in multiple variations (different colors, sizes, or flavors), Amazon organizes those options using a parent-child ASIN structure. The parent ASIN acts as an umbrella. It’s not a product you can actually buy, and it’s never priced. It simply groups the variations together into one listing page.
Each individual variation, like a medium blue t-shirt or a large red one, gets its own child ASIN. Those are the actual products customers add to their cart. The benefit of this system is that all child ASINs under the same parent share reviews, sales history, and search ranking. So a new color option added to an established listing immediately benefits from the reputation the other variations have built up.
Why ASINs Matter for Shoppers and Sellers
For shoppers, the ASIN is the most precise way to search for a specific product on Amazon. Typing an ASIN into the search bar takes you directly to that exact listing, which is useful when someone recommends a product and you want to find the exact same one rather than sifting through similar results.
For sellers, ASINs are central to how Amazon’s catalog works. Listing a product under the wrong ASIN can lead to listing removal or account issues. Sellers also use ASINs to track competitor pricing, monitor listing performance, and run advertising campaigns, since Amazon’s ad platform targets products by ASIN. If you’re researching products to sell, comparing ASINs is the standard way to evaluate specific listings rather than broad product categories.
ASINs are exclusive to Amazon’s platform. They have no meaning outside of it, unlike a UPC or ISBN, which works across retailers. If you’re selling on multiple platforms, you’ll use your UPC or EAN everywhere else and your ASIN only for Amazon.