GTIN / EAN / UPC Validator: Common Mistakes and Best Practices

Most problems with gTIN / EAN / UPC Validator aren't caused by not knowing what to do — they're caused by small, easy-to-miss mistakes that compound quietly over time. Here are the ones that come up most often.

Mistake 1: Copying a similar product's GTIN as a placeholder 'to fix later' — this immediately creates a false association between two unrelated listings.

Mistake 2: Ignoring check-digit validation and only checking that a code is the right length, letting typos through undetected.

Mistake 3: Not flagging genuinely GTIN-exempt products correctly, causing repeated feed rejections for items that were never going to have one.

The fix for most of these isn't more effort, it's a regular check. A few habits that prevent them from creeping back in:
- For products genuinely without a GTIN (custom, handmade, or pre-GS1 items), use the `identifier_exists: false` flag rather than leaving the field blank or fabricating a number.
- Re-verify GTINs after any product data migration — imports from spreadsheets are a common source of transposed or truncated digits.

Worth reading alongside this: our guide to product feed validation, which covers the adjacent side of the same part of a technical SEO audit.

GTIN / EAN / UPC Validator catches most of this automatically, which is the easiest way to stop these mistakes from shipping in the first place.

Everything in this guide runs directly in your browser — no signup, no install.