A phone can fail to recognise a QR code, recognise it but offer the wrong action, or read it correctly and then fail to load the linked page. Those are different problems. First observe whether the camera displays a link or other recognised content.
If a website address appears but the page fails, check that address separately using the website-loading guide. Regenerating the same code will not repair a broken destination. For a Wi-Fi QR code, recognition does not establish that the password or network security settings are correct.
Use the QR code generator with a short HTTPS address, a dark square pattern and a light background. Test on the intended phone before changing styling. Then change one feature at a time so that you can identify what affects reading.
For a printed item, test a physical proof at the actual size. A large preview on a desktop screen does not establish that a small glossy label will scan from the required distance. Different phones and camera apps can behave differently.
A QR symbol needs a clear margin around it, known as the quiet zone. DENSO WAVE’s guidance specifies four modules on each side. A module is one of the small units in the code, not a fixed number of millimetres for every symbol.
[[figure:qr-quiet-zone]]Do not crop away the margin to make the code fill a box. Keep nearby text, borders and decorative backgrounds outside it. When adding the code to a design, check the exported artwork as well as the original generator preview.
Small modules need enough printed or displayed detail to remain distinct. Dense data can create a more detailed code at the same overall size. Where possible, encode a concise destination you control rather than an unnecessarily long address with many parameters.
Keep strong contrast. A visually attractive colour combination can be difficult for a camera to distinguish. Avoid resizing in a way that blurs the modules, stretching the code into a rectangle or placing it across a fold, curved surface or reflective glare.
Dots and other decorative patterns may work well under some conditions, but successful scanning should be checked rather than assumed. The larger structural patterns help a scanner locate and interpret the symbol. Leave those structures intact instead of treating every square as optional decoration.
If a plain version works while a styled one fails, simplify the design before changing the destination. If neither works, inspect the exported size, content and print quality. Avoid using a third-party scanning app merely because an advert says it is required; modern camera support and supported content vary by device.
Confirm the full website address, including HTTPS and the intended path. Test the decoded destination before distributing printed material. A QR code does not itself guarantee that a site is legitimate, so readers should check the preview before opening an unfamiliar destination.
For Wi-Fi, compare the SSID, case-sensitive password, security type and hidden-network choice with the actual network. A QR code containing a Wi-Fi password should be shared only with the people meant to join that network. A guest network is usually easier to manage than printing a private household password in a public place.
For contact details, check how the receiving phone imports the fields. Different scanners support different actions, so successful recognition and successful import should both be tested.
A static QR code stores its content; it does not update itself after printing. A website at that address may redirect later, but that depends on maintaining the domain and service. Choose a destination you expect to keep, test it before publication and periodically check material that remains in circulation.
When asking a designer for a fix, send the original export, the intended physical size and the devices you tested. Use a non-sensitive example when sharing publicly. That is more helpful than a screenshot that has already been resized several times.