GTIN / UPC / EAN Validator
Validate retail barcodes against the GS1 check-digit algorithm — EAN-8, UPC-A, EAN-13, and GTIN-14 — with format detection and country prefix lookup. Everything runs in your browser.
Check digit calculator
Enter the digits without the check digit — the full code is returned.
ISBN-10 validator
How it works: starting from the digit left of the check digit, weights alternate 3, 1, 3, 1 moving right-to-left. The check digit brings the weighted sum to the next multiple of 10 — the same formula across UPC-A, EAN-8/13, and GTIN-14.
A valid check digit confirms the number is well-formed, not that it was issued by GS1 to your brand. Marketplaces like Amazon cross-check the GS1 registry — reseller codes can pass the checksum and still be rejected.