GTIN, brand, and the 'hidden SKU' problem
Google Shopping requires GTIN (universal product code) for most branded products. Meta prefers brand + category for catalog matching. Shopify's default feed skips both when a store hasn't filled them in. Result: 30-50% of SKUs are technically live but ineligible for Shopping ads. Fixing GTIN + brand attributes typically doubles Shopping campaign inventory overnight — same ad spend, more products showing.

