Glossary · Feeds & Merchant Center
What is a primary data source?
A primary data source is the feed that creates products in Merchant Center. Everything else — supplemental sources, rules — works on the products it contains, matched by product ID. If a product is not in a primary source, supplemental data about it is ignored.
What this comes down to
- Only primary sources add or remove products.
- Supplemental data updates a product only when its ID exists in a primary source.
- Platform apps (Shopify, WooCommerce) usually act as the primary source.
- Stable IDs in the primary source are what keep supplemental fixes attached.
What the primary source controls
The primary source carries the required attributes — ID, title, link, price, availability and so on — and any optional ones you include. When you connect a store through a platform app, that connection is typically your primary source, and you edit its contents in the store rather than in Merchant Center.
Google states that product data is only updated from a supplemental source when the supplemental file contains IDs that are in a primary source. The product ID is the join.
Categories in the primary source
If your platform lets you set google_product_category per product, the value travels in the primary source. If it does not — or setting it product by product is impractical — a supplemental sheet of ID plus category does the same job. The integration pages cover what each platform supports.
Before you change anything
Decide where the category should live, once. If your store platform can hold a Google category per product and the value flows into the primary source, set it there and let every future sync carry it. If it cannot, keep categories in a supplemental file — and in either case, start by exporting the product IDs exactly as Merchant Center shows them, because every later step depends on those IDs matching.
Questions
Can I have more than one primary data source?
Merchant Center supports several data sources. Each product should come from one primary source, and supplemental data is linked to the primary sources it applies to.
What happens if a product ID changes?
Supplemental rows keyed on the old ID stop matching, so their values no longer apply. Keep IDs stable, or regenerate the supplemental file.
Sources
Read next
- Supplemental data sourceA Merchant Center data source that adds or overrides attributes on products already in a primary source, matched by product ID; it cannot add or remove products.
- Product ID (id)The required feed attribute that uniquely identifies a product in Merchant Center, and the key that supplemental data sources match on exactly.
- Google Merchant CenterGoogle’s service for submitting and managing the product data behind Shopping ads and free product listings, organised into data sources of product attributes.
- How to override Google's automatic product category with a supplemental feedWhat a supplemental feed can and cannot change, when Google accepts a category override, and the exact two columns to submit in the file.