You may enter 7-, 8-, 12- or 13-digit barcodes. All forms support automatically calculating the final (checksum) digit. To do this, use a question mark instead of an actual digit, for example:
The default mode, "UPC / EAN", attempts to DWIM ("do what I mean"): If you pass it 7 digits or 8 digits starting with the digit 0, then it will generate a UPC-E barcode. If you pass it 8 digits not starting with the digit 0, then it will generate an EAN-8 barcode. If you pass it 12 digits, then it will generate a UPC-A barcode. Finally, if you pass it 13 digits, then it will generate an EAN-13 barcode.
You can force 8 digits to be generated as EAN-8 by selecting the mode "EAN-8".
You can force generation of UPC-E by selecting the mode "UPC-E". In this mode, you may also pass 12 digits, instead of 7 or 8, which will get compressed into the UPC-E form if the form factor is correct. (See this description of UPC-E for more information.) For example, if you ask to encode "04432000008?", then the generated UPC-E will be for the number "04432841".
All UPC/EAN barcodes support a 2- or 5-digit supplemental code, which appears to the right of the main code. To produce such a barcode, place a comma and then the supplemental digits after the main number to encode, for example:
To change the banner over the barcode, place a colon and a new message after the barcode number, for example:
If you want to suppress the banner entirely, place a colon after the number but nothing else, as in: