E-commerce sellers live in a world of tight rules. Amazon, Shopify, Walmart, eBay — each marketplace has its own checklist for product identifiers, and barcodes sit near the top of every one. Understanding what they actually want, and how to generate it for free, is a small investment that saves a lot of pain.
The GTIN Reality Check
Every barcode you print has two parts: the number (the GTIN — a globally unique product identifier) and the image (the visual bars). Most sellers confuse the two.
- The number must be purchased, officially, from GS1 if you want to list on major marketplaces. This is non-negotiable for brand-registered listings.
- The image — the visual barcode you print on a label — can be generated for free using our barcode generator from the official number.
Which Barcode Format Does Each Marketplace Want?
Amazon US: UPC-A (12 digits), or Amazon's FNSKU for FBA.
Amazon EU: EAN-13 (13 digits).
Shopify: UPC, EAN, or custom SKU labels — highly flexible.
Walmart Marketplace: UPC-A required, from GS1.
eBay: GTIN required for new products in most categories.
Etsy: No universal requirement, but barcodes help with inventory and in-person sales.
Step-by-Step: Print Retail Barcodes From Your GS1 Numbers
- Buy your GS1 company prefix. This gives you a block of unique numbers you can assign to each product.
- Assign a unique number to each SKU in your catalog.
- Open our free barcode generator and choose UPC-A or EAN-13 depending on your market.
- Paste the number and the generator validates and adds the check digit automatically.
- Download as SVG for your label printer or packaging designer.
- Print, scan, verify. Always test with a phone before the full run.
Shopify Merchants: SKU Labels for Inventory
If you are using Shopify's inventory system, you probably use internal SKUs like TSHIRT-BLU-M. These are not UPCs — they are your own codes. The best format for them is Code 128, which handles letters, numbers, and symbols.
Print Code 128 labels for your stock room, and pair them with a cheap Bluetooth scanner. Inventory counts that used to take half a day now take 20 minutes.
FBA Sellers: Understanding FNSKU
Amazon FBA has its own special barcode format — the FNSKU — that Amazon generates for you inside Seller Central. You cannot create this one yourself; it is assigned when you list a product for FBA. However, once you have the FNSKU label from Amazon, you can use any barcode generator to re-print it for larger runs.