Why rich black ruins a QR code
2026-08-28 · 4 min read
"Rich black" — mixing cyan, magenta and yellow ink under the black plate for a denser, richer-looking black — is standard practice for large solid areas in print. It's also a common way to accidentally break a QR code.
The problem is registration: on an offset or digital press, the four plates rarely land in exactly the same spot. On a photo or a solid background, a fraction of a millimetre of misregistration is invisible. On a QR code, where the whole signal is the sharp boundary between a dark module and a light one, that same fraction of a millimetre softens or fringes the edge — and the smaller the module, the bigger the effect relative to its size.
The fix is simple: use a single, pure black (K-only, 100%) for the code's modules, and keep any rich black to the surrounding artwork, not the code itself. If your print shop's proof shows any colour fringing around the modules under a loupe, that's rich black leaking into the code, not a printer error.