Despite its ubiquity, the humble QR code has been somewhat taken for granted by developers. The Quick Response (QR) code was invented by a subsidiary of Toyota to track parts across the manufacturing process.
Today, we usually use QR codes to get lengthy URLs onto our phones from walls, serviettes, business cards or even t-shirts; that is, any visible surface we can take a photo of.
In the case of a QR code, the reader has to work out how big the content holder is.
I have never seen a QR code like the one on the right, but it is describable within the system!