How do I find a users UUID in Minecraft?

Minecraft uses UUIDs (Universally Unique Identifiers) to identity users, every user in the game has one and this information is used in log files, error reports and permission settings. To find the UUID for a Minecraft User you can use a service like MinecraftUUID.com. All you need to do is enter the username of the user and you will be returned the UUID, skin and extra information if it is available.