Tools that show their rules
Every tool here publishes the complete list of checks it runs — with severities, plain-English explanations and official sources. Built for the edge cases quick scripts miss, and honest about what they cannot tell you.
Subject areas
Start here
A starting set, hand-picked for breadth — not a popularity ranking. This site has no analytics, so it does not know what is popular, and will not pretend to.
- GTIN / UPC / EAN ValidatorValidate barcodes in bulk: check digits, GS1 prefixes, Excel corruption, restricted ranges and placeholder codes.
- Google Shopping Feed ValidatorCatch Merchant Center disapprovals before you upload: required attributes, GTIN validity, identifier logic, price and enum formats.
- Excel Damage DiagnosticFind out what a spreadsheet broke in your column — and whether each value can still be repaired or is gone for good.
- Product Title CheckerCheck a title against every marketplace's length limits and style rules, with the problems highlighted on the words themselves.
- Invisible Character DetectorFind the zero-width spaces, BOM and look-alike characters hiding in your text — and see what each one is doing to your data.
- UN Number LookupSearch the Hazardous Materials Table by product name or UN number, and see every entry sharing that number with its own limits.