Generate RFC 4122 v4 UUIDs instantly

A UUID (Universally Unique Identifier) is a 128-bit value used to identify something — a database record, a session, a device — without needing a central authority to hand out the next number. The odds of two randomly generated UUIDs colliding are astronomically small.

They're the same concept. GUID (Globally Unique Identifier) is Microsoft's name for the same 128-bit structure defined by the UUID standard, RFC 4122. The two terms are used interchangeably in practice.

It refers to version 4 of the UUID specification, which generates the identifier from random or pseudo-random bits rather than a timestamp or hardware address. It's the most commonly used version because it requires no coordination and reveals nothing about when or where it was created.

Not mathematically guaranteed, but close enough for virtually any practical purpose. A version 4 UUID has 122 random bits, giving roughly 5.3 undecillion possible values — you would need to generate billions of UUIDs per second for a very long time before a collision became even remotely likely.

Yes, this is a common and well-supported pattern, particularly for distributed systems where multiple servers need to generate IDs independently without checking with each other first. The main tradeoff is that random UUIDs don't sort chronologically the way auto-incrementing integers do.