How long a QR code lasts outdoors
2 min read
A QR code fails outdoors for three reasons, and none of them is the code itself.
Ultraviolet light
Sunlight fades ink. A scanner does not read black and white, it reads contrast — and a code does not stop working the day it looks grey, it stops working the day the difference between the dark squares and the light ones falls below what a camera can separate.
This is why a cheap label on a south-facing stone can be gone in two summers while the same label on a north-facing one is still fine at five years. The material is the variable, not the weather.
What survives: pigment printed with UV-stable inks, or printed on the underside of a transparent layer so the light hits the layer rather than the ink.
Water at the edges
Freeze-thaw is the quiet one. Water gets under a lifted corner, freezes, expands and lifts it further. A winter does this a few dozen times.
What survives: an adhesive rated for outdoor masonry, applied to a clean dry surface above freezing, with pressure held long enough to bond. Most failures are fitting failures, not material failures.
Dirt
Pollen, algae, splashed soil. A code half-filled with green film will not read, and it is entirely reversible — a wipe with a damp cloth twice a year is the whole maintenance.
Worth saying plainly because families worry about the wrong thing: dirt looks like failure and is not.
What to look for when buying
- Printed under a protective layer, not on top of one.
- An adhesive named for outdoor stone or metal, not a general-purpose one.
- A replacement guarantee measured in years, and stated in writing. This is the most useful signal of all — a company that guarantees ten or twenty years of free replacement has priced in its own failure rate, which means it has measured it.
The failure that actually matters
A faded sticker is visible, annoying, and fixed by a replacement in the post.
The failure nobody sees is the other end: the address stops resolving because the service has closed. The code is pristine and leads nowhere. Ask what happens to the page if the company stops trading before you ask how long the sticker lasts.