Definition
Item group ID is the product feed attribute that tells Merchant Center which rows are variants of the same product. Every size, colour and material of one item shares the same value while keeping its own unique id, so Google can understand that it is looking at one product offered in several forms rather than at a shelf full of unrelated listings.
Four feed rows for one jacket in two colours and two sizes
- Row 1
- id SP-4410-NVY-M, item_group_id SP-4410, colour Navy, size M
- Row 2
- id SP-4410-NVY-L, item_group_id SP-4410, colour Navy, size L
- Row 3
- id SP-4410-OLV-M, item_group_id SP-4410, colour Olive, size M
- Row 4
- id SP-4410-OLV-L, item_group_id SP-4410, colour Olive, size L
- Shared across all four
- Title, description, brand, product category, price where identical, and the same item_group_id value
- Different on each
- The id, the variant attributes, the variant image, the availability and the link with its variant parameter
An illustrative product. The grouping value is arbitrary as long as it is stable and unique to this product, which is why a parent SKU or the platform's product id is the usual choice.
Why it matters
Item group ID matters because it changes what a shopper sees and what the store can measure. Grouped variants let Google present one listing with the available colours and sizes rather than four near-identical entries competing with each other, which is a better result page and a cleaner click. It also keeps availability sensible: when one size sells out, the product stays visible through its siblings instead of disappearing. On the reporting side, grouped items roll up in Merchant Center and in Shopping campaign reports, so a store can see how a product performs overall rather than trying to piece it together from variant rows. Google expects the attribute wherever variant attributes are submitted.
Where it goes wrong
- Giving every variant its own group value, which is the same as having no grouping at all and leaves the listings competing against one another
- Sharing one value across genuinely different products, such as an entire collection or a whole brand, which Google treats as a single item and reports as one
- Changing the value when a platform migration or a feed tool rewrites ids, which breaks the grouping history and can reset how the products are consolidated
- Submitting the group without the variant attributes that explain it, so Google is told these rows belong together but not what distinguishes them
- Sending the same image and the same variant landing page for every row, which makes the grouped listing show a colour the shopper did not choose
Questions about item group ID
Is item group ID required for Google Shopping?
It is required when a product comes in variants and you submit variant attributes such as colour, size, pattern or material. A product with no variants does not need it. In apparel especially, where size and colour are expected attributes, leaving the grouping out is one of the more common reasons a catalogue underperforms without producing an obvious error.
How does Shopify set item group ID in its Google feed?
The Google and YouTube channel sends each variant as its own row with the product's identifier as the grouping value, so the default behaviour is usually correct with no work. Stores that build a feed with a third-party tool set the mapping themselves, and the field to map is the parent product identifier rather than the variant SKU.
Can item group ID be the same as the product id?
Yes, and on most platforms it effectively is. The rule is that the id must be unique per variant row and the group value must be identical across the variants of one product and used by no other product. Using the parent product identifier for the group and the variant identifier for the id satisfies both conditions naturally.