Identifiers should come from trusted product data, not from a rule that fabricates a number to remove an error.
What a GTIN does
A GTIN is a manufacturer-assigned global trade identifier used to identify a specific product. Different formats include EAN, UPC, ISBN and ITF-14 depending on product type and market.
When the value is missing
Check manufacturer, supplier or product information sources first. A supplemental feed or joined source may contain the identifier even when the ecommerce platform does not.
When the value is invalid
Validate length and checksum rules, remove spaces or separators where the destination expects numeric values and make sure the identifier actually belongs to the product.
Do not substitute an internal SKU
An internal SKU and a GTIN are different identifiers. Mapping a SKU into the GTIN field may make the feed look complete while making the product data wrong.
Do not invent a GTIN
Google explicitly warns merchants not to guess or make up GTIN values. If you cannot verify the identifier, flag the product for review instead of fabricating data.
Use feed health to prioritise
A catalogue-wide view helps identify whether the problem is isolated to one supplier, product range or import source. That often leads to a better upstream fix.
Feednetic is designed to turn repeatable findings from this kind of audit into mappings, rules, enrichment workflows and validation checks rather than one-off spreadsheet fixes.