GA4 ecommerce events accept a long list of product attributes. Most setups send id, name, price, and quantity, and stop there. Two more fields, GTIN and brand, unlock additional reporting and improve cross-platform attribution. Both are free to send if you already have the data.

GTIN: the global product identifier

GTIN (Global Trade Item Number) is the standardised barcode identifier: UPC, EAN, ISBN. If you sell branded products, your supplier almost certainly provides a GTIN per SKU. Send it as item_id or as a separate item_gtin parameter (both work; the parameter version preserves your internal SKU as item_id).

items: [{
  item_id: 'SKU-A',
  item_name: 'Wireless Headphones',
  item_brand: 'Sony',
  item_gtin: '8806094800753',
  price: 149.99,
  quantity: 1
}]

Why GTIN matters

For Google Merchant Center integrations, GTIN is the canonical product identifier. Sending it improves matching with Merchant Center products, which improves Performance Max attribution, dynamic remarketing, and Shopping ad relevance.

For analytics, GTIN lets you compare sales of the same product across multiple sellers if your data ever feeds into a multi-retailer view.

Brand: the manufacturer name

item_brand is the manufacturer name. For multi-brand retailers, it lets you build "sales by brand" reports natively in GA4 without needing custom dimensions. For single-brand stores, it is less useful but still good practice for Merchant Center alignment.

Other useful product parameters

In your data layer

Push the full product object from your backend rather than reconstructing it client-side. The backend has the GTIN; the client-side data layer often does not, and adding it server-side via your tagging server is more reliable than asking the front-end to source it.

For the matching ecommerce migration

When migrating ecommerce events to server-side, audit your product payload at the same time. Adding GTIN and brand during the migration is much cheaper than retrofitting them later.