ASIN is an acronym that stands for “Amazon Standard Identification Number.” When you visit a product page on Amazon’s website, the URL contains this 10-character number. Sellers can also see it in the listing information.
The ASIN gets assigned to identify products within the Amazon’s catalog. It is guaranteed unique within each country’s marketplace. That way, sellers have opportunities to promote their goods without increasing the risk of a communications error.
Customers can type the ASIN into Amazon’s search box to pull up the specific item.

What if I Have Variations of the Same Product?

Amazon understands that many sellers have different colors or styles for the same product sold on their site. Sellers receive a parent ASIN in this circumstance to ensure all items stay together on the same page.
Sellers create their ASIN by using Amazon’s Add a Product tool. Limits apply based on total sales, creation history, and other screening factors. Once a business sees a revenue increase, the site allows for more new listings.
If a product is already sold on Amazon, sellers must locate the ASIN in use for it to create a listing. If a new one is required, that means the competition for the product is low. Sellers cannot create a new ASIN for an existing product.
Books follow a different set of rules when sold on Amazon. The ASIN must be the same as the assigned ISBN for the product. Sellers that list self-made items must also register their product for a Universal Product Code (UPC) or European Article Number (EAN) before the listing goes live. 
Understanding the ASIN process as a seller ensures that each item becomes searchable.