Long term technologies, waiting in the background (shkspr.mobi)

What I like about QR codes is that they have a special "alphanumeric" charset which has uppercase letters and numbers and : and / to make URLs. This encodes chars 5.5 bits per bytes and was a far-sighted choice for a standard defined in 1994.

I must admit, this is the kind of description that's enough to make me want to maybe get into ham radio someday.