QR codes went from a niche manufacturing tool to something on every restaurant table and product package in the span of a few years. The pattern looks random, but it's a precisely structured way of encoding data that a camera can read reliably, even at an angle or partially damaged.
What's actually encoded
A QR code stores data — usually a URL, but it can also be plain text, a phone number, a Wi-Fi network's credentials, or a contact card — as a grid of black and white squares representing binary data. The three large squares in the corners aren't part of the data; they're position markers that let a scanner instantly figure out the code's orientation, even if the photo is rotated or taken at an angle.
Why QR codes still work when partially damaged
QR codes include built-in error correction — extra redundant data encoded alongside the actual content, following the same principle as error-correcting codes used in data storage. Depending on the error correction level chosen when the code was generated, a QR code can still scan correctly even with up to roughly 30% of it obscured, smudged, or damaged. This is also why you'll sometimes see a logo placed in the center of a QR code — the error correction margin is deliberately large enough to absorb it.
The scanning process, briefly
A scanner locates the three corner markers to determine orientation and size, reads the grid of modules (the individual black/white squares) into raw binary data, applies error correction to reconstruct any unreadable parts, then decodes that binary data back into the original text or URL.
Make one in seconds
The QR Code Generator turns any URL, text, or Wi-Fi credential into a scannable code instantly, and the QR Code Reader decodes an existing QR code from an image if you need to check what one actually points to before scanning it with your phone.