EAN-13 barcode generator

Thirteen digits: a GS1 company prefix, your item reference, and a check digit calculated from the other twelve. Enter twelve and the last is worked out for you.

The check digit uses alternating weights of 1 and 3 across the twelve digits, summed, then subtracted from the next multiple of ten. That construction catches every single-digit error and most transpositions, which is why a mis-keyed barcode almost always fails rather than silently scanning as a different product. The part a generator cannot help with: the number itself must come from GS1, who allocate company prefixes. Inventing a number that happens to have a valid check digit produces a barcode that scans perfectly and may collide with a real product somewhere — fine for internal use, not for retail.