Why won't my QR code scan? A checklist

5 minute read · updated 2026-11-10

A code that won't scan is usually one of a short list of problems. Work through them in order: most are quick to spot once you know what to look for, and some can be fixed without reprinting.

First, find out what kind of failure it is

There are two different problems that look the same to the person holding the phone.

The phone doesn't react at all. No prompt, no link, nothing. This is a reading problem: the camera can't make out the code. Look at contrast, size, margin, glare and damage below.
The phone reads it, but the result is wrong. The link opens an error page, the Wi-Fi won't join, the contact card is missing fields. The code itself is fine; what is inside it is wrong. Look at the content section further down.

Telling the two apart saves a lot of time. If one phone opens a broken link, the print is fine and reprinting it will just give you another broken link.

Reading problems

Not enough contrast

Phones need a clear difference in brightness between the code and its background. Pale code colours, dark backgrounds, photos behind the code and colours of similar brightness all cause trouble. Photograph the code in black and white: if it turns into two similar greys, contrast is the problem. Our guide to QR code colours, logos and contrast goes into more detail.

Inverted colours

A light code on a dark background is read by many phones but not all of them, and often not by older scanner apps. If some people can scan it and others can't, this is a likely cause.

No margin

The empty border around a QR code, the quiet zone, should be at least four squares wide. When a code is printed right up against a border, an edge or other text, phones struggle to find where the code starts. You can sometimes rescue a printed code by trimming or masking whatever crowds it, or sticking it on a larger white label.

Too small for the distance

A code that works from 20 cm may not work from two metres. A rough rule is to make the code at least a tenth as wide as the scanning distance, so a code read from 1 metre should be about 10 cm across. Long web addresses make codes denser, so they need even more size. See how big should a QR code be.

Glare and curves

Glossy lamination, shop windows, screens and shiny bottles reflect light straight into the camera. Curved surfaces like cups and bottles bend the code so the squares no longer line up. A matt finish fixes glare; for curved items, keep the code small relative to the curve or put it on a flat part such as a label or a tag.

Damage and wear

Scratches, folds, fading in sunlight, dirt and peeling stickers all eat into the code's error correction, the spare information that lets a phone rebuild missing parts. A code with a large logo has less spare capacity left for damage. Outdoor codes fade faster than you would expect; check them every few months.

Too much detail

Codes holding a lot of text, like a full contact card or a very long link with tracking parameters, have many tiny squares. Printed small, or on rough paper where ink spreads, those squares merge together. Shorten what the code holds or print it larger.

Content problems

The link is wrong

A missing letter, an old domain, a page that has since moved, a link copied from a logged-in admin screen that nobody else can open. Scan the code and look at the full address the phone shows before it opens. Check it in a private browser window on mobile data, not on the office Wi-Fi where you might already be signed in.

The page is slow or not made for phones

If the code opens a huge PDF or a desktop-only page, people often give up and report that the code "didn't work". Test how long it takes on mobile data.

Wi-Fi won't join

Network names and passwords are case-sensitive, and some punctuation needs special handling inside the code. The security type must match the router. The Wi-Fi QR code guide walks through each of these.

Barcodes read the wrong number

For product barcodes, the most common cause is an invented number rather than one licensed from GS1, which a shop's system won't recognise. Our guide to product barcodes for small brands explains what retailers expect.

Can it be fixed without reprinting?

Sometimes. If a link points at your own website, you can put the right page at that address or add a redirect from the wrong address to the right one. Reading problems caused by surroundings, such as glare from a frame or a crowded edge, can often be fixed by moving or remounting the code.

Wi-Fi details, contact details and anything else stored in the code itself can't be changed after printing. A static code holds the content directly, so the only fix is a new code. If you expect to need changes later, read about static and dynamic codes before the next print run.

Preventing it next time

Scan the design on screen before you send it to print.
Print one copy on the real material, at the real size.
Test it where it will be used, in that light, from that distance.
Use at least two phones, ideally an iPhone and an Android.
Open the result and check it is exactly right: the right page, the right network, the right number.

Most failed codes would have been caught by step three.