Why Your QR Code Won't Scan, and How to Fix It

A QR code that will not scan is usually discovered at the worst moment: on a printed menu, a poster, or a box of business cards. The good news is that the causes are few and easy to check. Work through them in this order, because the early ones are the most common and the quickest to rule out.

1. Does the code itself work?

Open the original image on a computer screen and scan it with your phone. If it scans on screen but not on paper, the problem is the printing, so skip to step 5. If it does not scan even on screen, the design of the code is the problem. The QR Code Generator runs this check for you: it decodes every code it makes and confirms the result matches what you typed.

2. Is there enough contrast, the right way round?

Scanners look for dark modules on a light background. Brand colors are fine as long as the code stays clearly dark against a clearly light background: navy or deep green on white works, while light blue, yellow, pastel pink or mid-gray often do not, especially under warm indoor lighting. Inverted codes, with light modules on a dark background, look stylish and fail on a surprising number of phones and older scanner apps. If yours is inverted, flip it.

3. Is the quiet zone intact?

Every QR code needs an empty margin around it, ideally four modules wide. The scanner uses it to find where the code begins. Designers often trim it to tighten a layout, or place the code on a photo or a patterned background that intrudes into it. Put a plain light border back around the code and test again.

4. Is it too dense for its size?

The more a code holds, the more modules it needs, and the smaller each module gets at the same printed size. A long tracking URL can turn a simple 25-by-25 code into a 60-by-60 grid of tiny squares that a phone cannot resolve from across a room. Shorten what the code holds: remove tracking parameters you do not need, or point it at a short page on your own domain that redirects. Lowering the error correction level also reduces density, at the cost of less tolerance for damage.

5. Is it printed large enough, sharply enough?

• Size for the distance. A practical rule is that a code scans from about ten times its own width. A 2 cm code on a business card works at arm's length; a code on a poster read from 3 meters away needs to be about 30 cm across.
• Use a vector file. A small PNG enlarged by a printer gets soft, blurry edges between modules. Send the SVG, which prints perfectly sharp at any size.
• Watch the surface. Glossy laminate reflects light straight into the camera at some angles. Codes wrapped around bottles and cups bend out of shape. Matte finishes and flat surfaces scan best.

6. Is the logo or design covering too much?

A logo in the middle works only because error correction rebuilds the modules underneath it. Use the highest level, H, keep the logo to about a fifth of the code's width, and never cover the three large corner squares, which the scanner needs to locate the code. Rounded modules, gradients and custom corner shapes all eat into the same margin of tolerance, so test every stylistic change.

7. It scans, but nothing useful happens

Sometimes the code reads perfectly and the problem is what it says:

• The link is wrong or dead. A typo, a page that was moved, or an address without https:// that some phones treat as plain text rather than a link.
• The code was dynamic and expired. Many QR sites make codes that point at their own redirect service and stop working when a subscription ends. A static code contains your link directly and cannot expire this way.
• The WiFi details are malformed. A network name or password containing a semicolon, comma, colon or quote has to be escaped inside a WiFi QR code, or phones read a truncated password. The generator's WiFi shortcut handles this.

8. Rule out the phone

Finally, try a second phone. QR detection can be switched off in some camera apps' settings, a smudged lens defeats everything, and phones struggle to focus closer than about 10 cm, so pull back rather than pushing the phone closer to a small code.

A five-minute test before any print run

Print one copy at the final size on the final material. Scan it with two different phones, one of them older, from the distance people will actually stand, under the lighting where it will hang. It takes five minutes and has saved many a reprint.