XUID

Same as UUID, but what if it uses 36-based randomized alphanumerics (A-Z, 0-9)?

Possibility of UUID Collision: After generating 1 billion UUIDs every second for the next 100 years, the probability of creating just one duplicate would be about 50%. To put it another way, the probability of one duplicate would be about 50% if everyone owned 600 million UUIDs on Earth.