Barcode Generator

Pick the symbology the reader expects

EAN-13 and UPC-A are retail product codes, and both require a registered company prefix from GS1: you cannot invent one and expect it to work in a shop. Code 128 encodes arbitrary alphanumeric data and is the right choice for internal asset tags, shipping labels and anything not going through retail. Code 39 is older, less dense and still common in some industrial settings. QR codes hold far more data and scan from a phone camera, which linear barcodes do not do reliably.

Check digits are calculated, not chosen

EAN-13, UPC-A and several others end in a check digit derived from the preceding digits by a weighted sum. Enter twelve digits and the thirteenth is determined. Typing an arbitrary final digit produces a barcode that encodes cleanly and is rejected by every validating scanner, which is a confusing failure because the image looks perfect.

The quiet zone is part of the barcode

Linear barcodes need blank margin either side, typically at least ten times the narrow bar width. Designers routinely crop it to save space, and the result is a barcode that scans on the screen and fails on the printed carton. If a barcode works in testing and fails in production, the quiet zone is the first thing to check.

Size and print quality

Shrinking a barcode reduces the narrow bar width, and below roughly 0.25 mm most scanners struggle. Printing at low resolution or on absorbent stock blurs bar edges, which has the same effect. Retail has a defined magnification range for EAN-13 for exactly this reason, and printing outside it risks rejection by the retailer.

Contrast and colour

Scanners read reflectance, usually in red light. Dark bars on a light background is what works. Red bars are effectively invisible to a red-light scanner, and low-contrast pairings such as dark blue on black fail even though they look distinct to the eye. Black on white remains the only universally safe choice.