QR code guides
Everything we have worked out about making QR codes that still scan once they leave the screen — sizing, printing, formats, security and the measurements behind the usual advice.
How we test
Most writing about QR codes repeats the same handful of numbers from the specification. We wanted to know what those numbers mean in practice, so several of the guides here are built on measurements made for this site rather than on figures copied from elsewhere.
The bench is simple and deliberately boring: codes are generated with a reference encoder, damaged or degraded in a controlled way, passed through a simple camera model — a fixed optical blur, sensor noise and a small perspective error — and then decoded. Every data point is 40 to 80 attempts with different noise seeds, and the model is calibrated so that a clean code at ten pixels per module reads 100% of the time, which means any drop comes from the variable being tested.
Every figure is captioned with its method, and every result is reported as measured — including the ones that contradicted what we expected, such as decoders coping with far lower contrast than design guides recommend. One decoder is one decoder; a different reader will move the numbers. What the tests are good for is the order of things: which failure modes matter most, and which are folklore.
How QR codes work
The Anatomy of a QR Code
Every region of the grid, what it does, and which parts you can damage without consequence.
QR Code Error Correction Explained
What L, M, Q and H really buy you, measured on twelve thousand damaged codes.
How Much Data Fits in a QR Code
Real capacity figures for every version and level, and why the answer depends on what you encode.
Static vs Dynamic QR Codes
One puts the data in the image, the other puts it on someone's server. What each really costs.
How to Create a QR Code for Free
Three steps, and the four checks worth doing before anything goes to print.
Printing and quality
Best QR Code Size for Printing
One rule turns scan distance into millimetres, plus the resolution to send a printer.
How Small Can a QR Code Be?
The floor is set by the module, not the code. Measured: five camera pixels per module.
How to Print a QR Code
Paper, ink, contrast and the quiet zone: what actually decides whether a printed code scans.
PNG vs SVG QR Codes
Which file goes to a screen, which goes to a printer, and why the wrong one comes back blurry.
The Pre-Print QR Code Checklist
Twelve checks between the download and the print run. Ten minutes, one reprint avoided.
Why QR Codes Stop Working
Twelve reasons a code that scanned yesterday does not scan today, and which are fixable.
Formats and data types
How to Create a WiFi QR Code
The exact string format, the characters that must be escaped, and what iPhones and Android each do with it.
The vCard QR Code Format
The fields phones actually import, in the order they expect them, with a template you can copy.
QR Codes for Business Cards
A small card leaves little room. The size that still scans, and what to put behind it.
QR Codes for 3D Printing
Layer height, module size, contrast without colour, and why raised codes beat engraved ones.
Safety
Putting codes to work
QR Codes for Restaurant Menus
A table code that survives a change of menu, a change of prices and a change of supplier.
QR Codes for Google Reviews
Turn the review link into a code for the counter, and cut the taps between customer and stars.
QR Codes for Product Packaging
Curved surfaces, small labels and printing tolerance — the hardest place to put a code.
QR Codes for Real Estate Signs
Read from the pavement, from a car, in the rain: the size and the destination that work.
QR Codes for Flyers
Placement, contrast and the one line of text that decides whether anyone scans it.
QR Codes for Wedding Invitations
RSVP, directions, the gift list and the photo album — one small square instead of four inserts.