QR codes use Reed-Solomon error correction which means between 7% and 30% of the image data can be lost but the encoded text will still be readable. Digital TV

QR codes use Reed-Solomon error correction which means between 7% and 30% of the image data can be lost but the encoded text will still be readable. Digital TV / radio broadcasts use a similar system. These examples are taking a slice of that redundancy and replacing it with a design. This is a bit like using typography to make a URL look nicer but harder for a human to read.