Barcode generator
A linear barcode encodes digits or characters as a pattern of bars and spaces of varying width. Retail codes. EAN-13, UPC-A, EAN-8 and ITF-14. End in a check digit calculated from the ones before it, which is how a scanner knows it read the number correctly. Code 128 and Code 39 accept text as well as digits.
How to make a barcode
A retail barcode number is not something you can invent. GTINs are issued by GS1, and the first digits identify the company that owns them; printing a number you do not hold will scan, and will ring up as somebody else’s product. This generator will happily encode any valid number; whether you are entitled to use it is a separate question.
Questions
For EAN and UPC, digits are weighted alternately by one and three, summed, and the check digit is whatever brings the total to a multiple of ten. Enter the number without it and you will see the digit that gets added.
Because runs of four or more digits switch into Set C, which packs two digits into one symbol. Ten digits become seven symbols instead of twelve.
EAN-13 for retail outside North America, UPC-A inside it, Code 128 for anything internal, and ITF-14 for outer cases.
For laser scanning, keep the narrowest bar at about 0.33 mm or more. On screen that is roughly two pixels; in print, set the width from the physical label size.
Press Batch and paste a column of values. Each line becomes its own barcode, and invalid lines say why.