Funny QR Code Fails - "Oops" Moments Collected from Around the World
A QR Code Too Small for Anyone to Scan
You want to put a QR code on your business card, but there is no room. So you shrink the QR code to the extreme, and the usual result is a 5 mm square QR code printed timidly in the corner of the card. Even if you bring the smartphone camera as close as it will go, it cannot focus and cannot scan the code.
The minimum size needed to read a QR code depends on the scanning distance. If you hold a smartphone 10 cm away, you want the code to be at least 1.5 to 2 cm square. On a business card, keeping it at 2 cm square or larger is the safe choice, but if you put design first and make it too small, the QR code you went to the trouble of adding ends up as mere decoration.
The opposite also happens, with codes too large to read. If you paint one 10 meters square on the wall of a building, it does not fit in the camera's field of view from up close, and from far away the resolution is not enough. This is the scale trap: it is hard to find the "just right distance."
A Link That Leads to a 404 - The Saddest QR Code
You scan a QR code and "404 Not Found" appears. This is one of the patterns that often comes up among QR code fails. There are three main causes.
A typo in the URL: One character of the URL was wrong when the QR code was generated. The QR code itself works properly, but the page it points to does not exist. Noticing this after printing, when thousands of flyers have already been handed out, is a marketer's nightmare.
A site redesign: A URL that was valid when the QR code was printed changed during a site redesign. Brochures and posters can stay in use for a few months to a few years, so if the site structure changes during that time, the link breaks.
An expired domain: Someone forgot to renew a domain acquired for a campaign, and the domain expired. In the worst case, a third party may acquire the expired domain and the code may redirect to an unrelated site (in some situations, a malicious one).
One way to prevent these failures is to use a dynamic QR code. Because you can change the destination later, it can also cope with a mistyped URL or a site redesign.
A QR Code Shown on TV - The Problem of Vanishing in an Instant
A QR code appears on screen in a TV program or commercial, but it is shown for only 2 to 3 seconds and disappears while viewers are taking out their smartphones and opening the camera. This "QR code that vanishes in an instant" is a typical failure that frustrates viewers.
To scan a QR code, you need a series of actions: (1) pick up the smartphone, (2) unlock it, (3) open the camera app, (4) point it at the TV screen, and (5) wait for it to focus. This takes about 5 to 10 seconds. With 3 seconds on screen, scanning is impossible unless you are very well prepared.
When a TV program shows a QR code, you want to secure a display time of about 15 seconds. In addition, an advance notice such as "A QR code will appear. Please get your smartphone ready" raises the chance that viewers scan it successfully.
Printing Tragedies - Back to Front, Inverted Colors, Low Resolution
There is no end to the failures related to printing QR codes.
Printed back to front: The QR code gets printed as a mirror image (flipped left to right). It is hard to notice because to the human eye it still looks "sort of like a QR code," but readers determine orientation from the positions of the finder patterns, so they cannot recognize a mirror image.
Inverted black and white: For design reasons, the black and white of the QR code were inverted (white on black instead of black on white). In fact, many smartphone camera apps can also read QR codes with inverted black and white. However, some older models and third-party reader apps may not be able to read them, so standard black on white is recommended.
Low resolution: A QR code image was downloaded from a website and printed after being stretched large as is, so the module boundaries blurred and it could not be scanned. QR code images need to be generated at a resolution high enough for the print size (at least 300 dpi). If you generate them in a vector format (SVG), they will not degrade however large you scale them.
"Please Read the QR Code Aloud" - A Tragedy over the Phone
A funny story told on the internet goes like this: a customer called a call center and said "I can't read the QR code," and the operator replied "Then could you read aloud what is written in the QR code?" Of course, it is impossible to convey the black and white pattern of a QR code verbally.
What this funny story shows is that the QR code is something with a property that is rare in everyday life: "humans cannot read it, but machines can." Unlike letters, numbers, and barcodes (which can be read as a series of digits), a QR code is something whose content human cognition cannot grasp. This "opacity" is a security advantage (you cannot tell the content at a glance), and at the same time it is the cause of comical misunderstandings like this one.