Same brand and MPN but differing item group ID: how to fix it
What causes "Same brand and MPN but differing item group ID" in Merchant Center and how to fix variant grouping.
"Same brand and MPN but differing item group ID" means two listings share a brand and MPN, implying they're the same base product, but carry different item_group_id values, confusing Google's variant grouping. Align item_group_id for genuine variants, or correct the brand/MPN if they're actually different products.
What triggers it
item_group_id is how Google groups variants (different sizes, colours) of the same base product together. Brand and MPN together are meant to identify that same base product too, so when two listings agree on brand and MPN but disagree on item_group_id, Google reads it as a contradiction: your identifiers say "same product", your grouping says "different products".
This usually comes from a partial data update, one variant's item_group_id changed during a catalogue restructure while its siblings weren't updated, or from an MPN being reused across genuinely distinct products by mistake (which is the more serious of the two causes).
/tools checks variant relationships and identifier consistency together during enrichment, flagging cases where item_group_id, brand and MPN disagree before they reach Google.
Step by step
- Find the conflicting listings. Diagnostics will show which products share brand and MPN but disagree on item_group_id. Pull them up side by side.
- Decide whether they're genuinely the same product. If they're colour or size variants of one product, they should share one item_group_id across all variants.
- Align item_group_id for real variants. Set the same item_group_id on every variant of the base product, keeping GTIN unique per variant as usual.
- Correct brand or MPN if they're actually different products. If the listings are genuinely unrelated products, one of the brand or MPN values is wrong, not the item_group_id, fix whichever attribute doesn't match the real product.