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Supplemental feed

A supplemental feed is a secondary Merchant Center data source that adds or replaces attributes for products the primary feed already sends, matched by item ID.

How it works

The primary feed decides which products exist; a supplemental feed only brings values for them. It holds an id column and one column for each attribute you add or replace, with one row per product. Merchant Center matches each row to its product by item ID, together with the product’s feed label and language. A supplemental feed can’t add or remove products or work on its own. Typical uses: custom labels, a missing brand or GTIN, a title under test, and price and availability between full exports.

For each attribute, the default rule picks a value by going down an ordered list of sources. With the primary feed first, the supplemental one only fills empty fields. Item IDs are case-sensitive in Merchant Center, so a row for plt-0457 can miss the product PLT-0457. This is the item ID case trap. The setup, step by step, is in supplemental feeds in Merchant Center.

Where you see it

  • Merchant Center: Settings → Data sources → Supplemental sources, a tab that appears with the “Advanced data source management” add-on. A product source’s Attribute rules tab shows which source each attribute comes from.
  • Merchant API: a supplemental product data source linked to primary sources.

Example

Example store, not client data.

The tableware shop’s Google Sheet has two columns, id and custom_label_0 for the season, and 3,000 rows. A month later the shop has added 150 products to the store but no rows to the sheet. Of its 3,150 products, 150, or 4.8%, have no season label and land in the “everything else” group of any campaign split by that label.

Not to be confused with

  • Attribute rules — rules that reshape values already in your sources. A supplemental feed brings new values, product by product.

Right and wrong readings

  • Wrong: “We’ll add the missing products through a supplemental feed.” Right: a row with an ID the primary feed doesn’t send creates no product.
  • Wrong: “Once linked, the sheet overrides the export.” Right: if the primary source comes first in the default rule, the sheet only fills empty attributes.

Sources