As we announced on March 14, and in emails to all Product Search merchants, today we will begin requiring unique identifiers for products in all categories except for apparel, custom, and one-of-a-kind items. These requirements are part of an ongoing effort to make Product Search better for our users. Our unique identifier requirements enable us to build detailed product pages to help shoppers learn about products and compare prices from across the web. These unique identifiers are only required for Google Product Search, and this policy will not impact Google Commerce Search or AdWords ad formats.
We will be gradually enforcing this policy over the next few weeks, with full enforcement in effect on June 20th. During this time, products that do not have correct unique identifiers may not appear in our product listings. If you have products that do not have correct unique identifiers, we recommend that you make the necessary changes as soon as possible.
Please note that in the weeks after June 20th, we will begin disapproving the feeds of merchants who have a significant percentage of items that do not include the correct unique identifiers.
This will be difficult for smaller retailer to enforce. A summary of this article is that retailers that list products outside of the apparel and custom category items need two of the following three identifiers:
UPC, EAN, or JAN Brand MPN
Media needs UPC, EAN, or JAN
Books need ISBN (Either ISBN-10 or ISBN-13. Exceptions apply for books published before 1970.)