Standards-grounded learning
Product Identification & GS1 Guides
Understand product identifiers, GTIN formats, GS1 Application Identifiers and GS1 Digital Link before applying them with the free ProductPassKit tools.
Each guide is maintained by ProductPassKit from the primary GS1 sources linked on the page. Read our review method →
GTIN fundamentals
Build a precise foundation for product numbers, barcode terminology and check digits.
Fix Invalid GTINs in Merchant Center
Understand Google Merchant Center invalid GTIN warnings, check-digit failures, restricted prefixes, missing identifiers and safe product-feed fixes.
Read guide 5 min readGTIN Validation Test Vectors
Download 30 synthetic GTIN-8, GTIN-12, GTIN-13 and GTIN-14 test vectors in JSON or CSV to test checksum validators, leading zeroes and error handling.
Read guide 6 min readWhy Is My GTIN Invalid?
Diagnose invalid GTIN, UPC and EAN values: unsupported lengths, wrong check digits, missing leading zeroes and spreadsheet errors, with testable examples.
Read guide 7 min readWhat Is a GTIN?
Learn what a GTIN identifies, how GTIN-8, GTIN-12, GTIN-13 and GTIN-14 differ, and what a valid check digit does—and does not—prove.
Read guide 8 min readCompare GTIN-8, 12, 13 & 14
Compare GTIN-8, GTIN-12, GTIN-13 and GTIN-14 by length, barcode context, check digit and 14-digit representation, with clear examples.
Read guide 6 min readCalculate a GTIN Check Digit
Learn the GS1 modulo-10 GTIN check digit method with alternating weights, a verified GTIN-13 example and a quick way to check your result.
Read guide 6 min readUPC vs GTIN
Understand UPC versus GTIN, including the UPC-A and GTIN-12 relationship, identifier and barcode terminology, and 14-digit representation.
Read guide 6 min readEAN vs GTIN
Learn how EAN-13 relates to GTIN-13 and EAN-8 to GTIN-8, while keeping product identifiers, barcode symbols and check digits distinct.
Read guideConnected product data
Move from identifiers into structured GS1 data, web URIs and 2D carriers.
What Is GS1 Digital Link?
Learn how GS1 Digital Link expresses identifiers and attributes in web URIs, how QR codes carry them, and why syntax is not resolver conformance.
Read guide 8 min readGS1 Digital Link Examples
Explore validated GS1 Digital Link examples for GTIN, batch, serial and expiration data, with each AI and URI component explained clearly.
Read guide 8 min readGS1 Application Identifiers
Learn how GS1 Application Identifiers define data meaning and format, including AI (01), (10), (17), (21), fixed lengths and FNC1 separators.
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