A product identifier is a standardized code, usually a string of numbers, assigned to a commercial product so it can be universally recognized across supply chains, retail systems, and online marketplaces. The barcode on the back of nearly every item you buy in a store represents a product identifier, and the same concept extends to digital listings on Amazon, Google Shopping, and other platforms. These codes make it possible for manufacturers, distributors, retailers, and search engines to all refer to the exact same product without confusion.
How Product Identifiers Work
Every product identifier serves one core function: it gives a specific product a unique numeric fingerprint. When a cashier scans a barcode, the scanner reads that number and pulls up the correct price, description, and inventory data. When a shopper searches for a product online, marketplaces use the identifier to match listings from different sellers to the same verified item.
This matters because the same product might be sold by dozens of retailers under slightly different listing names. A product identifier cuts through that ambiguity. It tells every system in the chain, from a warehouse database to a Google Shopping result, that two listings are describing the same physical item.
Global Identifiers vs. Internal Codes
Product identifiers fall into two broad categories: global identifiers that stay the same no matter who is selling the product, and internal codes that a specific business creates for its own use.
A Global Trade Item Number (GTIN) is the international standard. GTINs are typically 12 to 14 digits, embedded in the barcodes printed on product packaging, and they are unique to a specific product and its manufacturer. The key feature of a GTIN is that it never changes as a product moves from manufacturer to distributor to storefront. Listing a GTIN on an online marketplace lends credibility to your products because search engines and shopping platforms can match your inventory against globally verified identifiers.
A Stock Keeping Unit (SKU), on the other hand, is an internal tracking code that a business creates for its own inventory management. SKUs are series of numbers and letters that can change depending on which business is handling the product. A retailer might build abbreviated details into a SKU, such as the brand, size, or color, making it easier to track stock and serve personalized recommendations to shoppers. Two different stores selling the same pair of shoes will share the same GTIN but use completely different SKUs.
Major Types of Global Product Identifiers
Several standardized formats exist under the GTIN umbrella, each tied to a specific region or product category.
- UPC (Universal Product Code): The standard in North America. Also called GTIN-12, it consists of 12 numeric digits and is the barcode you see on most products sold in the U.S. and Canada.
- EAN (European Article Number): Used primarily outside North America. Also called GTIN-13, it typically contains 13 numeric digits, though eight-digit and 14-digit versions exist. This is the most widely used format globally.
- JAN (Japanese Article Number): Used only in Japan. It follows the same GTIN-13 structure as the EAN and comes in eight- or 13-digit formats.
- ISBN (International Standard Book Number): Used globally for commercial books published since 1970. The older ISBN-10 format has 10 digits (the last digit may be an “X” representing the number 10), while the current ISBN-13 format has 13 digits and typically starts with 978 or 979. You can find it on the back cover of any book, usually above or near the barcode.
Despite the different names, these are all variations of the same idea: a globally unique numeric code tied to one specific product.
Why Online Marketplaces Require Them
If you sell products online, you will almost certainly encounter product identifier requirements. Google Shopping, Amazon, and other major platforms ask sellers to provide GTINs (or the equivalent UPC, EAN, or ISBN) when creating product listings. The platforms use these codes to verify that a product is real, match it against known manufacturer data, and group identical products from different sellers onto the same listing page.
Listings with valid product identifiers tend to perform better in search results. Without one, your product may not appear in filtered searches or may be flagged as unverified. Some platforms will reject listings outright if a GTIN is required for that product category and you leave the field blank.
Handmade goods, custom items, and certain vintage products are common exceptions. Most marketplaces allow you to indicate that no GTIN exists for these types of products.
How to Get a Product Identifier
If you manufacture or private-label a product, you need to obtain your own GTINs. These are only available through GS1, the nonprofit organization that manages the global barcode system. You join your local GS1 Member Organisation, which assigns you a company prefix. That prefix becomes the foundation for every GTIN you create for your products.
The process starts at the GS1 website, where you select your country and are directed to your regional office. Fees vary by country and by how many unique products you need to identify. In the U.S., for example, GS1 US charges an initial fee based on the number of barcodes you need, plus an annual renewal. Small businesses needing just a handful of codes pay less than companies requiring thousands.
If you are reselling products made by another manufacturer, you do not need to buy your own GTINs. The manufacturer’s existing UPC or EAN already applies, and you simply enter that code when listing the product. You can find it printed near the barcode on the product packaging, or request it directly from the manufacturer or distributor.
Be cautious about third-party barcode resellers that advertise cheap UPCs. Some marketplaces reject codes that cannot be traced back to a legitimate GS1 registration, which can result in suspended listings.
When Product Identifiers Matter Most
For a consumer, product identifiers are mostly invisible. You benefit from them every time a store scanner rings up the right price or a shopping site groups identical products so you can compare sellers.
For anyone selling, manufacturing, or distributing physical goods, product identifiers are foundational. They determine whether your products show up correctly in retail systems, whether online marketplaces accept your listings, and whether your inventory data stays accurate as products move through warehouses and fulfillment centers. Getting the right identifier in place before you list or ship a product saves significant headaches down the line.