QR codes were invented in 1994 by Denso Wave, a subsidiary of Toyota, to track automotive parts on the factory floor faster than a barcode scanner could. Barcodes only held a couple dozen digits and needed a straight-on scan; the two-dimensional grid Denso Wave designed could pack in far more data and be read at almost any angle in a fraction of a second — which is where the name "Quick Response" comes from.
The Wi-Fi QR code: one scan, no typing
One of the most practical everyday uses of a QR code has nothing to do with URLs. A Wi-Fi QR code encodes the network name, security type, and password in a single structured string; scanning it with a phone camera connects the device automatically, without anyone typing a long, mixed-case password by hand. It's the same underlying text format a router's admin page could print out, just wrapped in a shape a camera can read instantly.
Error correction levels
A QR code supports four error correction levels — L, M, Q, and H — which determine what percentage of the code's data can be damaged while still scanning successfully. The highest level, H, can recover up to roughly 30% of damaged data, which is exactly why a logo can safely be dropped into the center of a code, covering part of the pattern.
Why you'd need this
- Quickly generate a QR code for a link, a Wi-Fi network, or a business card.
- Pick a high enough error correction level if the code will be printed small or have a logo on it.
- Understand why a partially damaged or dirty QR code can still scan just fine.
The three corner squares — orientation markers
The three large squares in three of the QR code's four corners are position detection patterns, not decoration. They let a scanner instantly figure out the code's orientation in frame, even if the image is rotated or photographed at an angle — the fourth corner is deliberately left without one, so the scanner can also tell which way is "up."