Nine Things to Check Before a QR Code Goes to Print

The Nine Checks, in Order

Run these in sequence. The order matters because each check constrains the next: the destination sets the symbol version, the version sets the module count, and the module count is what turns a width in centimetres into a module size in millimetres.

1. Fix the Destination, and Keep It Short. A static code carries its destination in the pattern, so the URL cannot change after printing. Shorten it before generating: fewer characters means a lower symbol version, which means larger modules at the same printed width.
2. Set the Width From the Reading Distance. Divide the scanning distance by ten and never go below 2 cm. Size for the closest realistic reading position rather than the furthest - people walk up to posters, but a code sized for one metre cannot be read from three.
3. Check the Module Size in Millimetres. Divide the code's width by the number of modules across it, quiet zone included. Aim for 0.4 mm or more on coated stock and 0.5 mm or more on uncoated. If the number is under the floor, widen the code or shorten the payload.
4. Export at the Right Resolution, or as Vector. Vector has no resolution limit and is what a print shop asks for. For raster, 300 DPI at final size, with a whole number of pixels per module so no module edge lands mid-pixel and gets anti-aliased into grey.
5. Confirm the Quiet Zone Survives the Layout. Four modules of empty margin on every side. Check it against the artwork rather than the export: a code tucked against a rule, a photograph or the trim edge has lost the margin the exporter gave it.
6. Pick the Error Correction Level for the Job. Level M is the sensible default. Go to H only when a logo sits in the centre or the surface will be handled and marked, and accept that H puts more modules in the same width and so needs more of it.
7. Measure the Contrast, Do Not Judge It. Dark pattern on a light ground, around 7:1 for print. Light-on-dark works for some decoders and not others, so treat an inverted code as a design decision that has to be tested rather than a neutral choice.
8. Decide the Finish Before the Stock Is Ordered. Matte over gloss wherever the code will be read under a light source. Gloss and gloss lamination put a specular highlight across the symbol at exactly the angle people hold a phone.
9. Proof at Final Size on the Real Stock. Print one sheet at the size and on the material of the run, and scan it with two different phones in the light the code will actually live in. This is the only check that catches ink spread, and it is the one that gets skipped.

The Numbers in One Table

Everything above as figures, for checking a file against rather than reading through. Each row links to the page that establishes the number.

Where Each Check Is Explained in Full

This page is the sequence. Each of these owns one step of it, and the tools run the arithmetic rather than describing it.

• Size and module width. The minimum size for print has the charts by medium and the reason the floor sits where it does. The QR print size calculator turns a distance, a payload and a material into a width.
• Resolution and DPI. Resolution and DPI has the formula in both directions, and the DPI calculator runs it.
• File format. SVG vs PNG covers which one a printer wants and why the answer is not always vector.
• Quiet zone. The quiet zone explains what the four modules are for and what happens when a layout eats them.
• Error correction. Error correction levels covers L, M, Q and H, and the width each one costs.
• Capacity. QR code capacity explains why a longer URL produces a denser symbol, which is the step most size problems actually start at.
• Finish. Matte vs gloss printing covers lamination, varnish and the angle glare arrives at.
• Colour. The QR contrast checker gives the ratio for a colour pair before anything is printed.
• The finished file. The QR code validator measures contrast, quiet zone, module size and symbol version from the export itself, and reports the worst side rather than an average.
• What the code says. The QR code scanner reads the destination back out of the exported file, which is the one check a person cannot do by looking.

What the Checklist Does Not Cover

Three things go wrong in printing that no file check will catch, and they are worth knowing about before the run rather than after it.

• Ink spread on the actual press. Every printing process grows dark areas slightly. How much depends on the press, the ink and the stock, and the only way to know is the proof.
• Substrate colour. A code printed on kraft, on a coloured carton or on anything other than white starts from a lower contrast than the file suggests, because the light modules are the substrate.
• Curvature and handling. A code on a bottle, a cup or a folded leaflet is read off a curved or creased surface. Alignment patterns correct for some of that, and beyond a point nothing does.

If a code passed every check here and still fails on paper, that is the useful outcome: the fault entered after the file, which narrows it to the press, the stock or the placement. Why a QR code is not scanning works through those in order.