Damaged QR Codes Still Work 🤯 | QR Code Explained | Ep-3

A faulty QR code still scans perfectly when you feel it won't. It may have a scratch, a sticker on one side, or even a small part missing, and still your phone reads it correctly. — How does that happen? Welcome to episode 3 of Learning Interesting Things with Stra. Most people think a QR code is just random black and white boxes that take you to a payment link, website, or some stored information. But it is designed very smartly. First, your phone looks for the three big squares in the corners. These are like landmarks. They help the phone understand where the QR code is, which side is up and how big the code is. That is why even if you scan it from an angle, it can still figure things out. Now comes the second part. A QR code does not store only the actual data inside those black and white boxes. Some parts store the main message and some parts store extra backup information. Think of it like this. I send you amount is 50 but because of a scratch the last digit goes missing. Now you only see amount is five blank. Normally you would be confused but imagine I had also added a small clue. The digits should add up to five. Now you can guess the missing digit is zero. QR codes do a much smarter version of this using something called read Solomon error correction. So when a small part is damaged, the scanner detects that something is wrong and uses the backup data to rebuild the missing information. Depending on the QR code, it can recover from around 7% to 30% damage. So next time a scratch QR code still works, remember it is not luck. It is smart design, error detection and error correction working together.