Management codes and JAN/GTIN fields have explicit character rules
Management codes allow up to 50 characters and JAN/GTIN values up to 14. Mercari Shops documents ASCII letters, digits, hyphen and underscore as valid characters for both.
Blank cells are allowed because these fields are optional; populated cells are validated.
Trimming before validation can hide a real mistake
The previous implementation trimmed values before checking them, so a value such as ` SKU001` could slip through. The checker now validates the original cell for both length and allowed characters.
A surrounding half-width space is therefore an error even when the visible code looks familiar.
This checker does not force JAN/GTIN to digits only
Many JAN codes are numeric in practice, but Mercari Shops documents letters, digits, hyphen and underscore as allowed characters in this CSV field.
The checker follows that platform rule instead of inventing a stricter digits-only rule.
Bulk-update CSVs add ID dependencies
During bulk updates, SKU IDs and inventory-edit fields also need to line up correctly.
Use the Mercari Shops bulk-update checker when you are editing an exported update CSV.