Barcode generator

How to use it

1. Pick the format: CODE128 for your own labels, EAN-13 or UPC-A for retail.
2. Type the value. For EAN-13, twelve digits are enough: the thirteenth is calculated.
3. Set the bar width (2 or more prints reliably) and the height.
4. Download the PNG or SVG and test-scan the printed label.

The check digit is the part that goes wrong

An EAN-13 is not thirteen free digits. The last one is computed from the first twelve: each digit is weighted 1, 3, 1, 3 from the left, the weighted total is summed, and the check digit is whatever takes that sum up to the next multiple of ten. A scanner recomputes it on every read and rejects the code if it disagrees.

That is why this tool works it out rather than trusting what you typed. Enter twelve digits and it appends the thirteenth and tells you it did. Enter thirteen that do not agree and it refuses, and says which digit would have been right — because a mismatch usually means a typo somewhere in the middle of the number, and silently rewriting the last digit would turn a caught mistake into a barcode that scans perfectly as a different product.

Which format to use

EAN-13 and UPC-A are retail barcodes, and the numbers in them are allocated — a GS1 prefix identifies the company, and you have to be a member to have one. Making a valid EAN-13 here does not make it yours. For internal use — stock, shelf labels, asset tags, anything scanned only by your own system — CODE128 is the right answer: it takes letters and digits, has no length limit, and nobody has to allocate you a number.

Printing one that scans

Keep the bar width at 2 px or more, do not scale the image non-uniformly, leave the white space at each end alone, and print it black on white. Barcodes fail in exactly the ways you would expect — stretched, shrunk, low contrast, or printed over a texture — and a test scan of the real label takes ten seconds.