They: simply convert whatever input they get without the required checks for authenticity and mathematic calculations of the barcode number. These automatic barcode generators don't check if you entered an official unique number. This won’t seem like a problem at first, but once your products reach stores with a faulty barcode number and a useless barcode image, that is where you're in for trouble. Why? Because automatic barcode generators are not people who aim for high quality and care for your success!