Start by identifying what "not scanning" means. If the camera never recognises the square, investigate the image and scanning conditions. If a link appears but opens an error page, investigate the destination. If a Wi-Fi prompt appears but the connection fails, investigate the network information.
These failures look similar to a visitor, but they need different repairs. Use a simple control image and change one variable at a time before ordering replacement signs or business cards.
Classify the failure before editing
| What happens | First check | Useful next step |
|---|---|---|
| Camera does not recognise anything | Border, contrast, size and focus | Try a plain code on a bright screen |
| Link appears but page fails | Encoded URL and public access | Open the exact URL while signed out |
| Wrong page opens | Original input or redirect | Compare the decoded address with the intended one |
| Contact preview has wrong fields | Entered contact record | Test a shorter vCard on another phone |
| Wi-Fi code is recognised but will not connect | Network name, password and security option | Test the credentials manually |
Save the original file before changing it so you can compare outcomes. For a website code, also copy the full intended address into a browser directly. A working homepage does not prove that a particular menu or booking path exists.
Make a plain control code
Generate a second image containing the same information, with black modules, a white background and no logo. Keep a clear border. DENSO WAVE's symbol-area guidance specifies a four-module quiet zone on each side.
If the plain version works and the branded version does not, restore design features one at a time. Start with colour, then a modest logo, testing after each change. Do not interpret an error-correction percentage as permission to cover that percentage of the picture: logo placement and damage to important patterns matter.
If neither version works, reduce the content to a known public website address. This separates a scanning problem from an issue with a specific payload or device behaviour. The website generator is useful for this control test.
Compare the source file with the physical copy
If the file scans on a screen but the print does not, inspect the final printed size, surrounding artwork, ink quality, surface and reflections. A code stretched horizontally is no longer a square grid. A screenshot enlarged in a document may have blurry edges that were absent from the original.
Try a larger proof and remove glossy covers during diagnosis. If the uncovered print scans but the mounted sign fails, changing the encoded URL is unlikely to help. Adjust the mounting, lighting or material instead.
Use SVG where your print workflow supports it, or an adequately sized PNG. Our print-size guide explains how to reserve room for the whole symbol and test it at its actual viewing distance.
Check permissions and redirects on link destinations
A cloud document may open on your phone because you are signed in as its owner. Test the link signed out and, when appropriate, on mobile data. Confirm that the destination is intended to be public before changing its sharing settings.
For printed menu cards, keep the original address alive when replacing a PDF. For a profile link, check whether a username change invalidated it. A static code has no built-in expiry, but a destination can disappear or a third-party redirect can stop operating.
Record a clear pass condition
Before returning the material to use, write down the final file, payload, date, tested devices and physical placement. A pass means the intended action completes under realistic conditions—not merely that the camera detects a pattern once.
For Wi-Fi, use the guest-network test. For menus, use the update checklist. Recheck after changes to the destination, router or printed design so a solved issue does not return unnoticed.