A Global Trade Item Number (GTIN) is the unique numeric identifier used to identify a product across the global supply chain. GTINs are managed by GS1, the international standards organization, and are the foundation of barcode systems used in retail, ecommerce, and supply chain management. Different geographies and product types use different GTIN formats — UPC, EAN, ITF — but all are part of the same underlying standard.

Common GTIN formats

UPC-A (12 digits): the standard North American format. Most products sold in US retail carry a UPC-A barcode.
UPC-E (8 digits): the compressed UPC format used on small packaging where space is limited.
EAN-13 (13 digits): the standard international format used outside North America. Most products sold globally outside the US carry an EAN-13 barcode.
EAN-8 (8 digits): the compressed EAN format for small packaging.
ITF-14 (14 digits): used on shipping cartons and outer packaging, not individual consumer units.

Why ecommerce brands need GTINs

Marketplace requirements. Amazon, Walmart, Target, and other major marketplaces require GTINs (usually UPCs) for most product listings. Brands without GTINs can't list on these channels.
Google Shopping and ad feeds. Google Merchant Center requires GTINs for many product categories to qualify for Shopping ads and free Shopping listings.
Retail wholesale. Most retailers require GTINs for stocked products. Wholesale relationships generally can't proceed without them.
Inventory and supply chain. EDI feeds, warehouse management systems, and 3PL operations all use GTINs as the identifier that connects systems.
Brand protection. Authentic GTINs assigned to a brand's products help distinguish legitimate items from counterfeits in marketplace settings.

How to get a GTIN

GTINs come from GS1, the only legitimate source. The process:

Apply for a GS1 company prefix. The prefix is the brand-specific portion of every GTIN the brand assigns. Annual fee, scaled by company size.
Allocate GTINs to products. Once the prefix is established, the brand assigns specific GTINs to each SKU using GS1's online tools.
Generate barcode artwork. GS1 provides barcode-generation tools, or a brand designer can create the barcode artwork for packaging.

Avoid "barcode resellers." A wide ecosystem of third-party sellers offer "cheap UPCs" purchased before GS1 changed its policies. These unofficial GTINs cause problems with Amazon, Google, and major retailers, who increasingly require GS1-issued GTINs traceable to the registered brand owner. Buying a "cheap UPC" today often means re-doing the work later through GS1.

GTIN vs. SKU

GTINs and SKUs solve different problems:

GTIN: a global identifier that's the same for every retailer and channel selling that exact product. Standardized externally.
SKU: the brand's internal identifier for a specific product variant. Defined by the brand, used in their own systems, often differs from one brand's SKU format to another's.

A single product needs both: the GTIN connects it to external systems; the SKU connects it to internal operations.

The mistake that costs the most time is treating GTINs as a listing task rather than a data task. One GTIN belongs to one sellable variant — a size or color change is a new GTIN, and reusing one across variants causes duplicate-listing errors that are painful to unwind after inventory is live. Assign the numbers in the product record before any multichannel selling work begins, so marketplace feed integration reads them rather than reverse-engineering them later.

A correctly assigned GTIN only pays off once it’s flowing into a clean, current product feed — a duplicate or missing GTIN in the feed causes the same listing errors as never assigning one in the first place. For how to structure and maintain that feed so it keeps marketplace and Shopping listings approved, see this guide to Shopify product feed setup and optimization.