Glossary · Feeds & Merchant Center
What is the product id attribute?
The id attribute is a product’s unique identifier in your Merchant Center data. It is required, it must be unique, and it is the join key for supplemental data: a category row only lands on a product when its ID matches exactly.
What this comes down to
- Every product needs a unique
id. - Supplemental rows must match the primary ID exactly — no trimming, no case changes.
- Platform apps generate their own ID format; copy it from Merchant Center, not your store admin.
- Changing IDs detaches every supplemental value keyed on them.
The join key for everything supplemental
Google’s instruction for supplemental sources is to match your Product ID from the primary data source exactly. A difference in case, a stray space, or a prefix your platform adds will make the row match nothing, silently. The category you meant to send never arrives.
The safe habit is to export IDs from Merchant Center itself — the products list or a report — rather than rebuilding them from your store’s SKU column. Platform integrations frequently build the feed ID from more than the SKU.
Keeping IDs intact in bulk work
Spreadsheet tools love to “help”: long numeric IDs become scientific notation, leading zeros vanish. Import ID columns as text. The Bulk Mapper reads each cell as the text it finds and writes your ID column back into supplemental-feed.csv as it read it — it cannot recover an ID a spreadsheet already rounded, so fix that before you export.
IDs in the Bulk Mapper’s output
The upload-ready supplemental-feed.csv is only written when you map an ID column, because a category row without an ID has nothing to attach to. Map the column that holds the Merchant Center ID — not a handle or a SKU, unless your feed really uses it as the ID — and the file comes back with that column and google_product_category, nothing else.
Questions
Is the product id the same as the SKU?
Not necessarily. Many stores use the SKU, but platform apps often generate their own format. The ID that matters for supplemental data is the one Merchant Center shows for the product.
Why is my supplemental feed not updating products?
The most common cause is IDs that do not match exactly. Also check the feed label and language, which must match the primary data.
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.
- Feed labelThe label (shown as the data source label) that groups product data in Merchant Center; supplemental data must match it, along with the language, to apply.
- Primary data sourceThe Merchant Center data source that defines which products exist and supplies their core attributes; supplemental sources can only modify products it contains.
- 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.