Understanding Unique Product Identifiers (UPIs)

Google Merchant Center classifies commercial products using three primary identifiers: Brand name, Global Trade Item Number (GTIN/UPC/EAN), and Manufacturer Part Number (MPN). Omitting these identifiers severely reduces your product impressions across Google Shopping.

Formatting Barcodes Correctly in Schema

A common mistake is storing barcodes in generic text fields without declaring the barcode length. Google expects specific schema keys: gtin12 for US UPC codes, gtin13 for international EAN codes, and gtin14 for wholesale cartons.

What to Do If You Sell Custom or Handmade Goods

If you manufacture custom apparel, original artwork, or private-label products without official barcodes, do not invent random numbers. Instead, assign a unique MPN and provide your brand name in your JSON-LD schema.

Code Example: Google-Compliant JSON-LD

{
  "@context": "https://schema.org",
  "@type": "Product",
  "name": "Leather Travel Duffel",
  "brand": { "@type": "Brand", "name": "NomadLeather" },
  "mpn": "NOM-DUF-01",
  "gtin12": "810023456789"
}
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Frequently Asked Questions

Where do I add GTIN barcodes in Shopify admin?

In your Shopify admin, go to Products, select an item, scroll down to the Inventory section, and enter your 12 or 13-digit sequence in the Barcode (ISBN, UPC, GTIN) field.

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