What Is Universally Unique Identifier (UUID)?

You may have heard of "fingerprints," but did you know there's also a unique identifier for Internet objects and data? It's called the UUID, and it's just like a fingerprint. You can't change your fingerprint, and you can't change the UUID of an Internet object or data. If you think about it this way: You have a phone number that identifies you when you call someone, but if someone else has the same phone number as you, they wouldn't be able to call themselves. They'd have to ask for your permission first—and then only if you're okay with it will they be able to call themselves by your number. The same thing happens with the UUID: If two different objects have the same UUID, they can't use each other's numbers without asking permission first. The UUID, or "Universally Unique Identifier," is one of the most important and widely used data in modern computing. Many software companies, including Microsoft and Apple, employ UUIDs as components of globally unique identifiers (GUIDs). The ext2/ext3 file system in Linux uses UUIDs. UUIDs are based on a 128-bit value derived from several well-known sources of randomness. These sources include the computer's MAC address and system time. The result is a string of 64 hexadecimal digits—a value that any other computer can't duplicate. UUIDs are like cats: they're not easy to get, but once you have one, it's yours for life. UUID stands for "universally unique identifier," a special kind of number that exists only once in the world and never changes. UUIDs are used for digital things like web services, computer systems and files—in other words, anything that needs to be identified as itself. A UUID comprises three parts: a reference to the network address of the machine that generated it, a time stamp, and an arbitrary component (which is just another word for "random"). The timestamp ensures that two different hosts won't produce the same UUID at the same time—and because network addresses change every time you switch computers or restart your router, it also means that every computer has a unique UUID!