A GTIN or ISBN fails identifier validation
In the reportGTIN/ISBN fails length or check-digit validation
structured_data_gtin_checksum_invalid · Issue
A captured product identifier has an invalid length, character pattern, placeholder or check digit.
Severity: Medium. Correct the product identifier.
Why it matters
An accurate identifier helps consumers distinguish the product from other products.
What to do
- Compare the property, raw identifier and validation reason with the actual product packaging or publisher’s identifier.
- Correct the identifier; preserve leading zeros as a string. Remove an invented placeholder rather than guessing a replacement.
When to leave it as it is: A sku equal to a valid identifier is an annotation, not proof of an error.
What we read
We read the page’s captured HTML and its JSON-LD, Microdata and RDFa declarations without executing JavaScript or fetching remote contexts. The finding preserves the property, validated value, original declaration and source byte positions.
Incomplete capture, an unresolved reference, contradictory values or a form outside the supported parser means not checked. It never demonstrates a correction.
We check gtin8, gtin12, gtin13, gtin14 and ISBN values offline. A checksum mismatch records computed and declared check digits.
ISBN separators are normalized for validation. Numeric GTIN literals that may have lost leading zeros remain not checked.
Example & evidence
Illustrative correction; this is not a live audit.
"gtin13": "4006381333932""gtin13": "4006381333931"Confirm & check again
Check for yourself: Compare the reported property with the HTML served at this URL. Validate the corrected markup with the appropriate structured-data test.
Check again: Full audit — Run another full site audit. A correction is confirmed only for the same page with sufficient captured coverage and no remaining violation. Missing coverage does not close the finding.
Limits & sources
A valid checksum does not prove assignment, ownership or a match to this product; no identifier database is queried.
This rule does not verify the accuracy of sku or mpn and does not replace required-field validation.
Confidence: High The finding records an exact offline validation reason. It does not establish Google indexing, ranking or rich-result display.
Sources
- Google, Product structured data — Explains product identification in structured data. Checked 3 October 2026.
- GS1, How to calculate a check digit manually — Describes weighted modulo-ten check-digit calculation. Checked 3 October 2026.
Editorial review: 2 November 2026