QR Codes (aka Quick Response Codes) were created in 1994 by a Japanese company Denso Wave who used them for tracking parts & vehicles. QR Codes have been used for many things since then, but most notably for check-ins during the COVID-19 response (at least here in Australia).
The QR Codes essentially carry only text, with a maximum of 7,089 numeric characters (4,296 for alphanumeric). The magic of "scanning and somethin happens" only happens because the QR Code Reader interprets the text and works out what to do.
The phrase "QR Code" is registered trademark of Denso Wave Incorporated (more QR info here).
QR Code Text Input
QR Code Output
Note: It is possible to hijack a QR Code, so keep your wits about you. There are two ways to do this that I'm aware of:
- The simple way is to stick a different QR Code over the top of the real one.
- The slightly more interesting way makes use of the difference in the way that different QR Code readers read the pattern. You can place a smaller QR Code within a larger one and half the people scanning will end up with the right data, and half the new data.