QR Code with Logo

Covering part of a QR code with a logo sounds like it should break it, and the fact that it doesn't comes down to a feature built into the format. QR codes carry Reed-Solomon error correction, meaning a portion of the data is redundant and the code can be reconstructed even when some of it is unreadable. Placing a logo deliberately consumes some of that budget.

The four correction levels

There are four levels, usually written L, M, Q and H, recovering roughly seven, fifteen, twenty-five and thirty percent of the code respectively. Higher correction means more redundancy, which means more modules for the same data, which means a denser code. Level H is the usual choice for a code carrying a logo, because it leaves the most room to obscure.

The important caveat is that the budget is shared. Error correction exists to handle real-world damage: print defects, scratches, glare, a fold in a leaflet. A logo that consumes the entire allowance leaves nothing for any of that, so a code that scans perfectly on screen can fail on paper. Staying meaningfully below the theoretical maximum, rather than at it, is what makes a logo code reliable in the field.

Three areas that must never be covered

Error correction protects the data modules. It doesn't protect the structural patterns a scanner uses to find and orient the code in the first place. The three large squares in the corners are position markers, and obscuring any of them means a scanner cannot locate the code at all, regardless of correction level. The timing patterns running between them and the format information beside them are similarly critical.

This is why logos belong in the center. The middle of a QR code is data, which error correction can rebuild, while the corners are structure, which it cannot.

Quiet zone and contrast

A QR code needs a clear margin around it, conventionally four modules wide, so the scanner can tell where the code ends. Designs that crop tightly to the edge or place the code on a busy photograph frequently fail for this reason alone, with the code itself perfectly intact.

Contrast matters just as much, and inverting the colors is the usual mistake. Many scanners expect dark modules on a light background, so a light-on-dark code can be unreadable on hardware that reads a conventional one instantly. Testing on more than one device, including an older phone, is worth the few minutes before anything goes to print.