Which symbology
| Format | Holds | Used for | | --- | --- | --- | | EAN-13 | 12 digits + check | retail products, worldwide | | EAN-8 | 7 digits + check | small packages where EAN-13 will not fit | | UPC-A | 11 digits + check | retail in the US and Canada | | Code 128 | any printable ASCII | logistics, internal labels, serials |
If the code is for your own systems, Code 128 is almost always the right answer: it takes letters as well as digits, it is compact, and no registry is involved.
How the check digit works
Take the twelve digits of an EAN-13. Starting from the right of the payload, multiply alternately by 3 and 1, add the results, and the check digit is whatever brings that sum up to the next multiple of ten.
For 590123412345 the weighted sum is 53, the next multiple of ten is 60, so the
check digit is 7 — giving 5901234123457. This tool does that for you, and if
you paste a full code with a wrong last digit it tells you and shows the correct
one.
Printing that actually scans
- Keep the quiet zone. Light margin either side, at least ten narrow-bar widths. This is the number one cause of failed scans.
- Do not stretch. Changing the aspect ratio distorts bar widths. Scale both dimensions together, or increase height only.
- Print dark on light. Red bars are invisible to a red laser scanner.
- Test before ordering. Print one, scan it with a real scanner, then order the run of ten thousand.
Everything runs locally
The barcode is drawn in your browser and the value is never transmitted, which matters when the value is a serial number or an internal SKU.
Questions
What is the check digit?+
The last digit of an EAN or UPC, calculated from the ones before it. It lets a scanner catch a misread instantly. Paste twelve digits and this tool works out the thirteenth; paste thirteen and it verifies the one you have and corrects it if it is wrong.
Can I invent my own EAN codes?+
You can generate a valid-looking one, and it will scan. You cannot use it in retail: EAN and UPC numbers are allocated by GS1, and the prefix identifies the company that owns it. Using a number allocated to someone else will collide in retail systems. For internal use — warehouse bins, asset tags — use Code 128, which nobody allocates.
Why does my printed barcode not scan?+
Almost always the quiet zone: the plain light margin on both sides. Scanners need roughly ten times the narrow-bar width, and a design that crops flush to the bars removes it. After that, the usual causes are printing too small, low contrast, or scaling that lands bar widths between printer dots.
SVG or PNG?+
SVG for anything going to print or into a layout — it stays exact at any size. PNG for a screen or a system that will not take vectors. The PNG here is rendered at twice the on-screen size, because a barcode printed at 1× often will not read.