BarcodeGenerator

Different jobs expect different formats:

• Code 128: any letters, numbers and symbols, packed tightly. The best choice for stock labels, shipping, tickets and anything internal.
• EAN-13: 13 digits, the standard retail barcode in most of the world.
• UPC-A: 12 digits, the retail barcode in the US and Canada. Scanners read it as an EAN-13 with a leading 0.
• EAN-8: 8 digits, for packs too small for an EAN-13.
• Code 39: capitals, numbers and a few symbols. Older and wider than Code 128, but still required by some industrial and government systems.

The last digit of an EAN or UPC number is a check digit, worked out from the others. Scanners recalculate it on every scan, so a misread bar is caught instead of ringing up the wrong product.

To work it out, the digits are multiplied by 3 and 1 in turn, starting from the right, and added up. The check digit is whatever brings the total up to the next multiple of 10. Type one digit fewer than the full length and the tool adds it; type the full number and the tool checks it.

To sell in shops or on marketplaces like Amazon, yes. Retail EAN and UPC numbers come from GS1, the body that runs the system, with a prefix tied to your company. A made-up number can belong to someone else's product, and big retailers check.

Drawing the barcode is the free part: once you have your numbers, any generator, this one included, makes the picture. For anything that stays inside your business, like stock, assets or tickets, you don't need GS1 at all. Use Code 128 with your own codes.

Print dark bars on a light background; black on white is safest. Red bars often don't scan, because many scanners use red light.

Keep the blank margin on both sides, called the quiet zone, and don't squash the barcode to fit. If it's too wide, lower the bar width rather than stretching it. Download the SVG for print, so the bars stay sharp at any size.