If you're selling products online, you've likely encountered a confusing alphabet soup of product identifiers: GTIN, UPC, EAN, ASIN, ISBN. Understanding these codes is essential for managing inventory, listing products on marketplaces, and maintaining accurate product data across channels.
UPC: Universal Product Code
The Universal Product Code (UPC) is a 12-digit identifier printed as a barcode on commercial products sold primarily in the United States and Canada. You've seen these barcodes on virtually every retail product—they're scanned at checkout to identify the product and look up its price.
UPCs serve several critical functions:
- Point of sale identification: Allows retailers to quickly scan and process products
- Inventory tracking: Enables accurate stock management across locations
- Product verification: Ensures the correct product is shipped to customers
- Marketplace listings: Required by most major retailers and marketplaces for product catalog matching
GTIN: Global Trade Item Number
GTIN is an umbrella term for a family of product identification standards maintained by GS1, the global standards organization. GTINs come in several formats:
- GTIN-12 (UPC): 12-digit codes used primarily in North America
- GTIN-13 (EAN): 13-digit European Article Numbers used internationally
- GTIN-14 (ITF-14): 14-digit codes used for cases and pallets
- GTIN-8 (EAN-8): 8-digit codes for small products with limited packaging space
- ISBN: International Standard Book Numbers for books and publications
To obtain GTINs, you must register with GS1 (gs1us.org in the United States). There's an initial registration fee plus annual maintenance fees. The cost depends on your company's revenue and how many unique products you need to identify.
ASIN: Amazon Standard Identification Number
The Amazon Standard Identification Number (ASIN) is Amazon's proprietary 10-character alphanumeric identifier. Every product in Amazon's catalog has a unique ASIN, which Amazon uses for:
- Organizing its product catalog
- Matching sellers to existing product listings
- Search and discovery within the Amazon platform
- Tracking product performance and reviews
ASINs are automatically generated when you create a new product listing on Amazon. If you're listing a product that already exists in Amazon's catalog, you'll use the existing ASIN.
Do You Need All Three?
The identifiers you need depend entirely on where and how you sell:
Amazon-Only Sellers
If you sell exclusively on Amazon, you technically don't need UPCs for most categories. Amazon will generate ASINs for your products. However, some categories require GTINs, and having UPCs makes listing matching easier and more accurate.
Multi-Channel Sellers
If you sell across multiple platforms (Amazon, Walmart, your own Shopify store, retail partners), UPCs become essential. They're the common identifier that connects your product data across systems and marketplaces.
Retail Distribution
If your products will be sold in physical retail stores, UPCs are absolutely required. No major retailer will stock products without proper barcodes registered through GS1.
Private Label Products
For private label sellers, you'll need to decide whether to obtain legitimate GTINs through GS1 or use Amazon's Brand Registry GTIN exemption (if you qualify). We strongly recommend proper GS1 registration—it provides credibility, enables multi-channel selling, and avoids potential issues with marketplace compliance.
Common Mistakes to Avoid
- Buying cheap UPCs from resellers: These often cause listing issues because they're not properly registered to your company in the GS1 database
- Reusing UPCs across variations: Each unique product (size, color, configuration) needs its own UPC
- Ignoring GTIN requirements: Google Shopping and many marketplaces increasingly require valid GTINs for product listings
- Not planning for growth: If you might sell in retail or internationally someday, set up proper identifiers from the start
Recommendations
For most growing ecommerce brands, we recommend:
- Register with GS1 and obtain a company prefix if you manufacture or private label products
- Assign unique UPCs to every product and variation
- Maintain a master product database with all identifiers (UPC, ASIN, internal SKU) linked
- Use inventory management software that syncs identifiers across channels
The upfront investment in proper product identification pays dividends as your business scales across channels and markets. For more on multi-channel selling, see our guide on diversifying from Amazon to DTC, and learn about Walmart vs Amazon fee structures to evaluate marketplace expansion.