// Supplemental feed builder
Supplemental feeds — patch attributes without rebuilding your primary feed
A supplemental feed lets you add or override specific product attributes without changing your primary feed. They're the cleanest way to fix missing GTINs, add custom labels, fix product types, and override sale prices — without touching your store.
// Find feed gaps
Scan your store to identify supplemental-feed opportunities
Our independent scanner reads your product pages and flags missing or weak attributes — the inputs you'd want to fill with a supplemental feed. Free, no signup.
Find my feed gaps →When to use a supplemental feed
- Missing GTIN, MPN, or brand on many items — fill them once without editing every product page.
- Custom labels for Shopping campaign segmentation — tag products as "high margin", "seasonal", etc.
- Override product titles or types — fix Google's auto-categorisation when it's wrong.
- Override sale prices — run a sale through GMC without changing your store.
- Add color, size, gender, age group for apparel — patch missing required attributes in bulk.
The 4 ways to deliver a supplemental feed
- Google Sheets — simplest. Build a sheet, share with the Merchant Center service account, schedule.
- Scheduled fetch — host an XML/TSV file on your server, GMC fetches it on schedule.
- Manual upload — one-off uploads for occasional fixes.
- Content API — for stores that already use the API for primary feed.
How matching works
The supplemental feed needs an ID column that matches the offer ID in your primary feed. Every other column you include is an attribute that will override or add to the primary feed for that product.
Common mistakes
- ID column does not match the primary feed offer IDs.
- Target country/language not selected — the supplemental feed only applies to the country it targets.
- Adding a column with wrong attribute name (case-sensitive).
- Forgetting to schedule the feed for daily fetch.