Missing MPN
MPN (Manufacturer Part Number) is a unique identifier assigned by the manufacturer to distinguish their specific product model. Unlike a GTIN (which is globally standardized via GS1), MPNs are assigned by each manufacturer independently. Google uses MPN — especially when paired with brand — as an alternative product matching signal when no GTIN is available. For products where GTINs don't exist (custom parts, industrial components, accessories without barcodes), MPN + brand is the required identifier pair.
Limited performance due to missing value [mpn]Impact: Missing MPN is a Warning, not a hard Error — products can still serve without an MPN. However, when a product has no GTIN and no MPN, Google can't match it to its catalog at all, which significantly reduces impression volume and ad performance.
Root Causes
- 1The product doesn't have a GTIN (missing-gtin error) and also has no MPN — leaving Google with no way to identify the product in its catalog.
- 2Your platform has an 'SKU' field but no dedicated MPN field, and your feed plugin is either not mapping any identifier, or incorrectly mapping your internal SKU as MPN.
- 3Products were imported from a supplier without MPN data, so the field was never populated.
- 4You set identifier_exists = 'no' (correct for one-of-a-kind items) but are selling branded/manufactured products that do have MPNs from the manufacturer.
- 5Your feed template was built without an MPN column — it was never added because the person building it confused MPN with SKU.
Fix by Platform
- 1Shopify doesn't have a native MPN field. You need to add it as a product metafield.
- 2Go to Shopify Admin → Settings → Custom data → Products → Add definition. Create a metafield with namespace 'google', key 'mpn', type 'Single line text'. This is the recommended namespace for Google Shopping metafields.
- 3On each product page, scroll to the new 'Google MPN' metafield and enter the manufacturer's part number exactly as it appears on the product/packaging/manufacturer website.
- 4In your feed app (Simprosys, AdNabu, DataFeedWatch): go to field mappings → map the 'mpn' attribute to your newly created 'google.mpn' metafield.
- 5Alternatively, many merchants use a custom product tag formatted as 'mpn:MODEL123' and parse it in feed rules — but the metafield approach is cleaner and more maintainable.
{% comment %} Access MPN metafield in Shopify Liquid {% endcomment %}
{{ product.metafields.google.mpn }}When This Doesn't Apply
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Frequently Asked Questions
What's the difference between MPN and SKU?+
SKU is your internal inventory number — it has no standardized meaning outside your business. MPN is the manufacturer's own part number for the product model — it's consistent across all retailers selling that product. If you search 'Nike model number Air Max 270' you'll find the MPN on Nike's website and on the product tag. SKU is not a valid substitute for MPN in Google's feed.
My products don't have MPNs — they're generic or unbranded. What do I do?+
Set identifier_exists to 'no' in your feed. This is the correct way to tell Google that no standard identifier exists for this product. Do not invent an MPN or use your SKU. For truly generic/unbranded products, having identifier_exists = 'no' is valid and doesn't penalize your listings.
Where do I find the MPN for a product?+
Check these in order: (1) the product packaging or manufacturer label, (2) the manufacturer's website product page (usually in specs or the URL), (3) your supplier's product data sheet. The MPN is often the model number, part number, or style code printed on the product itself.
Does submitting MPN along with GTIN help performance?+
Yes. More identifiers give Google more signals for catalog matching, which broadens your product's eligible query matching. Google's own guidance says 'the more product identifiers you provide, the better'. If you have all three (GTIN + MPN + brand), always submit all three.