Printing a code so it actually scans
Most codes that fail in the wild fail for one of six reasons, and all six are decided before it goes to press.
Why this is the surface that punishes you
Everything else you publish can be fixed after somebody complains. A print run cannot. By the time a code comes back from the printer too small, or laminated to a shine, or with its margin trimmed off, the mistake exists five thousand times and the only remedy is money.
So the rules below are not craft, they are insurance — and the last one is worth more than the other five together. Print a proof at final size on the final stock and scan it with an ordinary phone, at the distance and in the light people will really have. That takes about a minute and catches everything.
Use vector — SVG or PDF — for anything larger than a flyer. A PNG scaled up in a layout program produces soft module edges, and soft edges are what a camera struggles with.
See it happen
What you can do with it
Size: about a tenth of the reading distance
2 cm on a table tent, 3 cm on a flyer, and a great deal more on a poster people read from across a room. Below about 2 cm you are relying on a good camera and a steady hand.
Dark on light, with real contrast
A light code on a dark background works on many phones and fails on some, which is the worst kind of failure because it looks fine when you test it. A mid-grey on white is also thinner in print than it looks on screen.
The quiet zone is part of the symbol
Four modules of blank margin, kept clear of text, borders and the edge of the page. Crowding it is the single most common cause of a code that scans on screen and not on paper.
Test the actual print, not the PDF
Final size, final stock, an ordinary phone, the real lighting. It takes a minute and catches every problem on this page.
Getting there
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Export vector
SVG or PDF. A scaled-up PNG has soft edges.
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Place it with its margin
Nothing in the quiet zone, including borders.
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Proof at final size
On the final stock, not on office paper.
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Scan it like a stranger would
Arm's length, ordinary phone, the real light.
More in the same place
How to do it
Questions
Why did my code work on screen but not in print?
Nine times in ten, the quiet zone. A border or a caption crept into the margin, which the eye forgives and a scanner does not.
Can I print a code on a curved surface?
Yes, larger and flatter than you think you need. A code on a shiny curve can be unreadable at every angle somebody naturally tries.
What resolution do I need?
Use vector and the question does not arise. If it has to be a raster, aim for 300 dpi at final size and never scale it up afterwards.
Does colour reduce reliability?
Only through contrast. A strongly coloured code on white is fine; a pale one on cream is not, and the studio measures the difference before you download.
Try it with one code
The free plan has no expiry and asks for no card, and the analytics behind it are the same ones a paying customer gets.
Free forever for one person. No card, and 10,000 scans a month included.