Symptoms
- Invalid value: GTIN [gtin]
- Incorrect or unsupported GTIN
- Leading zeroes disappear after spreadsheet editing
- A limited-performance warning for identifier data
Common causes
- The value is not 8, 12, 13, or 14 digits after allowed separators are removed
- A spreadsheet converted the identifier to a number
- One GTIN was copied across variants
- A seller invented a GTIN for a product that has none
How to check
- Preserve GTIN as text
- Check numeric characters and supported length
- Confirm each variant uses its manufacturer-assigned identifier
- Distinguish a missing optional GTIN from an invalid supplied GTIN
How to fix
- Restore the manufacturer-assigned GTIN
- Reformat the spreadsheet column as plain text before export
- Remove a guessed value rather than inventing an identifier
- Correct the source system if the same bad value will be regenerated
Prevention
- Keep identifier columns as text
- Do not reuse a parent GTIN for distinct variants
- Run a basic format check on the exported feed
Evidence and scope
This page passed TinkerVane's Evidence Gate: a documented real problem, clear search intent, a matching file-level capability, a duplicate-content check, and an explicit overclaim boundary.