GTIN & Product Identifiers: The Complete E-Commerce Guide

What Are Product Identifiers?

A product identifier is a standardized numeric code that uniquely identifies a specific product worldwide. The umbrella term is GTIN (Global Trade Item Number), managed by the GS1 organization. Every barcode you see on retail packaging encodes a GTIN.

Different regions and product types use different GTIN variants, but they all serve the same purpose: giving every product a globally unique fingerprint that machines can read instantly.

Why AI Agents Care About GTINs

When a shopper asks an AI agent to find a product, the agent needs to do more than just search by name. It needs to verify the product exists, match it across retailers, and compare pricing confidently. GTINs make all of this possible.

Here is what AI agents use GTINs for in agentic commerce:

• Cross-retailer matching: A GTIN lets the agent confirm that the "Nike Air Max 90" on your store is the exact same product listed on five other retailers, enabling accurate price comparison
• Authenticity verification: GTINs registered with GS1 prove a product is legitimate. Agents deprioritize listings that cannot be verified
• Review aggregation: By matching GTINs across sources, agents pull together reviews from multiple retailers to build a complete picture of product quality
• Knowledge graph construction: Google's Shopping Graph and similar systems use GTINs as the primary key to connect product data from feeds, websites, and marketplaces into a unified product entity

Without a GTIN, an AI agent cannot confidently recommend your product. It might find your listing, but it cannot verify it against other sources. That uncertainty means the agent will favor a competitor whose product it can verify.

How to Find Your GTINs

Most products already have GTINs assigned. The challenge is finding them and getting them into your store data. Here are the four main sources:

From the Manufacturer

This is the easiest path. Check the product packaging for a barcode. The number printed below that barcode is the GTIN (usually a 12-digit UPC or 13-digit EAN). If you cannot find it on packaging, contact your manufacturer or brand rep directly. Most manufacturers maintain a catalog of GTINs and will provide them on request.

From GS1

If you are the manufacturer or brand owner and your products do not yet have GTINs, you need to register with GS1. Visit gs1.org to get started. The cost for small businesses in the US is $250 for initial registration plus $50 per year, which covers up to 10 GTINs. Larger packages scale up from there. This is the only legitimate way to get new GTINs assigned to your products.

From Product Databases

Sites like Barcodelookup.com and UPCitemdb.com maintain large databases of existing GTINs. Search by product name, brand, or MPN to find the GTIN for products you resell. These databases are especially useful when manufacturers are slow to respond or when you are onboarding a large catalog of third-party products.

From Your Distributor

Wholesale invoices and distributor catalogs often include UPC or EAN codes alongside product listings. Check your purchase orders, distributor portals, and catalog spreadsheets. This is frequently the fastest way to get GTINs for your existing inventory without contacting each manufacturer individually.

Platform Implementation

Once you have your GTINs, you need to add them to your e-commerce platform so they flow through to your product feeds and schema markup automatically.

WooCommerce

WooCommerce does not include a native GTIN field, but adding one is straightforward. Install the EAN for WooCommerce plugin (free) or use Rank Math SEO's built-in Product Schema GTIN field. Both add a GTIN input to the product editor under the Inventory tab. Once populated, the plugin outputs the GTIN in your Product schema markup and makes it available for feed plugins like Product Feed PRO to map to Google Merchant Center.

For the complete WooCommerce setup, see our WooCommerce AI readiness guide and the WooCommerce platform page.

BigCommerce

BigCommerce has a native GTIN/UPC field built into the product editor. Navigate to Products > Edit Product > Product Identifiers section. You will see fields for UPC/EAN, Global Trade Item Number, and MPN. Fill in the GTIN field and BigCommerce automatically includes it in your Google Shopping feed integration and storefront schema output.

See our BigCommerce AI agent optimization guide and the BigCommerce platform page for additional setup details.

Magento / Adobe Commerce

Magento does not ship with a dedicated GTIN attribute by default, but its flexible attribute system makes adding one simple. Go to Stores > Attributes > Product, create a new attribute called "gtin" with input type Text Field, and assign it to your default attribute set. Then populate the field on each product. For schema output, configure your SEO extension (such as Amasty or Magmodules) to map the GTIN attribute to the gtin property in Product JSON-LD.

See our Magento AI readiness guide and the Magento platform page for the full walkthrough.

GTINs in Google Merchant Center

Google Merchant Center treats GTINs as a critical product attribute. Products without GTINs face reduced visibility in Shopping results and Google AI Mode recommendations. In many categories, missing GTINs trigger an "insufficient product identifiers" warning that suppresses your listing entirely.

To get GTINs into your Merchant Center feed, map your platform's GTIN field to the gtin attribute in your feed specification. If you use a feed plugin (Product Feed PRO for WooCommerce, native integration for BigCommerce), this mapping is usually automatic once the GTIN field is populated in your product editor.

For stores using supplemental feeds, create a spreadsheet with two columns: id (your product ID) and gtin (the GTIN value). Upload this as a supplemental feed in Merchant Center to add GTINs without modifying your primary feed. Learn more about feed optimization in our product feed checklist.

Handling Products Without GTINs

Not every product has a GTIN. Custom-made items, handmade goods, private label products without GS1 registration, vintage items, and one-of-a-kind pieces legitimately lack standardized identifiers. Google and AI agents accommodate this, but you need to handle it correctly.

In Google Merchant Center, set identifier_exists to false for these products. This tells Google that the product genuinely does not have a GTIN, rather than that you simply have not provided one. The distinction matters: products marked as having no identifier are accepted, while products that should have identifiers but are missing them get flagged and suppressed.

When identifier_exists is false, provide the brand name and a descriptive title as alternative identifiers. If available, include the MPN (Manufacturer Part Number) as well. These fallback identifiers help AI agents partially match your product, though visibility will still be lower than products with valid GTINs.