UUID Generator
A UUID is a 128-bit identifier so large that generating one randomly is, for all practical purposes, guaranteed to be unique — no coordination between systems needed, which is exactly why they're used everywhere distributed systems need unique IDs.
Inputs
Result
673dd135-4d22-4284-ae08-5c813e957aad
Version 4, randomly generated
How the uuid generator works
This generates a version 4 UUID: entirely random except for a few fixed bits that mark its version and variant, per the RFC 4122 standard.
The format is a 36-character string (32 hex digits plus 4 hyphens) arranged as 8-4-4-4-12 characters.
Example format
- A version 4 UUID looks like: 3fa85f64-5717-4562-b3fc-2c963f66afa6.
- The '4' in the third group and the leading digit pattern in the fourth group are fixed by the version-4 specification; every other hex digit is randomly generated.
Common mistakes to avoid
Assuming UUIDs are sequential or sortable by creation time
Version 4 UUIDs are purely random — they carry no information about when they were generated and won't sort into creation order. Time-ordered use cases typically need a different UUID version (like version 7) instead.
Worrying about collision as if it were a realistic practical risk
With 122 random bits (after the fixed version/variant bits), the probability of two independently generated version-4 UUIDs colliding is astronomically small — far below the risk of, say, hardware failure — making it safe to treat as effectively unique for virtually any application.
Frequently asked questions
Why use a UUID instead of a simple incrementing number for IDs?
UUIDs can be generated independently by many different systems or services simultaneously with no risk of collision or need for central coordination — an incrementing counter requires a single authoritative source to avoid duplicates.
What does 'version 4' specifically mean?
It indicates the UUID is generated using random or pseudo-random numbers, as opposed to other versions that incorporate timestamps, MAC addresses, or namespace-based hashing instead.
Are UUIDs guaranteed to be unique, or just extremely likely to be?
Strictly speaking, they're probabilistically unique, not mathematically guaranteed — but the probability of a collision is so vanishingly small under normal random generation that it's treated as effectively guaranteed in practice.
Can a UUID be used as a password or security token?
It's not designed for that purpose — while unpredictable, UUIDs aren't necessarily generated with cryptographic-grade randomness guarantees across every implementation, so dedicated secure token generation is preferable for security-sensitive contexts.
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