GTIN Digit Checker

A GTIN digit checker verifies barcodes and identification codes by checking or computing their check digit. It supports GTIN-8 (EAN-8), GTIN-12 (UPC-A), GTIN-13 (EAN-13), GTIN-14, ISBN-10, and ISBN-13, each validated against its own format-specific check digit algorithm.

Multiple codes, one per line, validate in a single batch, with each row of results showing the code, its detected format, validity, and expected check digit. A format can be fixed to one of the six types, or left on auto-detect, which infers the format from the code's length.

Hyphens and spaces within a code are stripped automatically before validation, so an ISBN entered as 978-0-13-468599-1 or 978 0 13 468599 1 is processed the same way.

GTIN formats (8, 12, 13, and 14 digits) use an alternating weight algorithm: factors of 1 and 3 are applied to the digits, summed, and taken modulo 10, and the check digit is the value needed to bring that total to the next multiple of 10. ISBN-10 uses a weighted sum with multipliers descending from 10 to 2, taken modulo 11; a remainder of 10 produces the check digit X. ISBN-13 follows the same algorithm as GTIN-13, since ISBN-13 codes are a subset of the EAN-13 standard.

Take the 11 data digits of a UPC-A (GTIN-12) code: 0-3-6-0-0-0-2-9-1-4-5. The odd positions (1st, 3rd, 5th, 7th, 9th, 11th), digits 0, 6, 0, 2, 1, and 5, sum to 14 and carry a weight of 3, giving 42. The even positions (2nd, 4th, 6th, 8th, 10th), digits 3, 0, 0, 9, and 4, sum to 16 and carry a weight of 1, giving 16. The total is 58; the next multiple of 10 is 60, so the check digit is 60 minus 58, or 2. The full, valid UPC-A code is 036000291452.

A CSV with codes in the first column loads directly into the batch text area. After validation, an export writes the code, detected format, status, and expected check digit for each entry back out to CSV.

Barcode and ISBN validation applies across retail, publishing, logistics, and data management workflows where accurate product identification codes prevent costly errors.

• Retail inventory management: Verifying that product barcodes scanned into a point-of-sale or inventory system carry correct check digits before committing them to the database reduces misidentified items and checkout errors.
• E-commerce product listing: Validating GTIN-12 and GTIN-13 codes before submitting product feeds to marketplaces such as Amazon, Google Shopping, or Walmart avoids the barcode rejections those platforms issue for invalid check digits.
• Publishing and library cataloging: Confirming ISBN-10 and ISBN-13 codes on book metadata records ensures that catalog entries, MARC records, and online bookstore listings reference the correct edition.
• Supply chain and logistics: Checking GTIN-14 codes on shipping containers and case packs verifies that outer packaging identifiers are consistent with inner product GTINs, preventing warehouse mispicks and shipment mismatches.
• Data migration and cleanup: Batch-validating a CSV of thousands of product codes from a legacy system identifies which entries need correction before loading into a new platform.
• Barcode label printing: Validating the numeric code before printing physical barcode labels catches transposition errors or truncated digits that would render the printed barcode unscannable.
• GS1 compliance auditing: Batch-checking an entire product catalog for valid structure and correct check digit against GS1 standards produces a report of non-compliant entries for correction.