Why are Irish number plates so much longer than British ones, despite the population being much smaller? What letters can you use on a Greek number plate? How do you drive a Japanese-registered car abroad, when the number plate is full of kanji and kana? Why do some people give Belgian cars with five-character plates a wide berth? Are those supercars with Arabic number plates you see in West London even legal? I've always been a bit obsessed with vehicle registration plates. I like spotting the hidden information in them, but I also like seeing the decisions encoded in their formats, and how those have played out over time. Everywhere seems to have come up with its own solution to the same problem, they're all different, and seemingly innocuous decisions can have significant impacts later on. These superficially trivial identifiers turn out to be much more than that, intersecting design, politics, information encoding, and even questions of identity. They're also, I hope to show, fun, and can make us all feel better about having to live with the consequences of bad choices we made in the past.