Putting a logo in a QR code without breaking it
It works because of error correction, and it fails when you spend more of that than the print run needs. Here is where the line is.
Why a logo works at all
A QR code carries redundant data so it can be read when part of it is damaged — a crease, a coffee ring, a thumb. Four levels exist, tolerating roughly seven, fifteen, twenty-five and thirty per cent loss. A logo in the middle is deliberate damage, and the correction is what absorbs it.
How much is safe
At the highest level, a logo covering up to about a fifth of the symbol's area is comfortable. That is not the whole thirty per cent, and the difference is the margin that survives the real world: ink spread on uncoated stock, a fold through the corner, a scan at forty degrees in bad light.
Cover a third and it will still scan on your desk, from a screen, at full size. That is not evidence. Print it at the size it will actually be and try it on the worst phone in the office.
Where to put it
Centred. The three big squares in the corners are the finder patterns and the timing rows between them are how a reader works out the grid — a logo touching any of those is not a damaged code, it is an unreadable one. The centre is the safest region because it holds data that redundancy can rebuild.
Keep the quiet zone
The blank margin around the symbol is part of the symbol: four modules' width, clear of text, borders and the edge of the page. Adding a logo makes people tighten the layout, and crowding the quiet zone is the most common cause of a code that scans on screen and fails on paper.
A shorter destination is a sturdier code
Fewer characters means fewer modules means larger modules at the same printed size — and larger modules survive everything. This is the quiet argument for a dynamic code: it encodes a short redirect rather than a long campaign URL, so the same 2 cm of card carries a coarser, more forgiving symbol.
Questions
How big can a logo be in a QR code?
About a fifth of the symbol's area at the highest error correction level. The format tolerates roughly thirty per cent loss, and the gap between the two is the margin that survives print — ink spread, folds and awkward scanning angles. Larger will scan on a screen and let you down on card.
Does adding a logo make a QR code less reliable?
It spends redundancy that was there for damage, so yes, a little — which is why the correction level goes up when you add one. Kept to a fifth of the area and centred, the practical difference is nil. Placed over a corner pattern, the code is not damaged but unreadable.
Why does my QR code with a logo scan on screen but not in print?
Usually one of three things: the logo is too large and print has eaten the remaining margin, the quiet zone around the symbol was crowded by the layout, or the code is simply too small for the distance. A useful rule is that the symbol wants to be about a tenth of the distance it is read from.
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