UUID v4 Generator

Generate RFC-4122 compliant version 4 UUIDs

Click "Generate UUID v4" to start

Bulk UUID v4 Generation

Understanding UUID Version 4

UUID version 4 is defined in RFC-4122 and is the most commonly used UUID type. It relies on random or pseudo-random numbers for generation, providing excellent uniqueness without requiring coordination between systems.

UUID v4 Format

xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx

Example: 550e8400-e29b-41d4-a716-446655440000
                        ^    ^
                        |    └── Variant (8, 9, a, or b)
                        └── Version (always 4)

All UUID Versions Compared

Version Name Generation Method Use Case
v1 Time-based Timestamp + MAC address When you need time ordering
v2 DCE Security Timestamp + MAC + UID/GID DCE environments (rare)
v3 MD5 Hash Namespace + name (MD5) Deterministic from input
v4 Random Cryptographic random General purpose (most common)
v5 SHA-1 Hash Namespace + name (SHA-1) Deterministic from input
v7 Time-ordered Timestamp + random Database indexing, sorting

Why Choose UUID v4?

  1. Universal support - works in every language and platform
  2. Privacy - doesn't expose MAC address or timestamp
  3. Simple generation - no coordination needed between systems
  4. Cryptographically secure - unpredictable values
  5. Proven reliability - decades of production use

UUID v4 vs UUID v7

UUID v7 is a newer standard that provides time-ordered UUIDs. Choose based on your needs:

  • Use v4 when order doesn't matter and you want maximum compatibility
  • Use v7 when you need chronological ordering or better database index performance

Frequently Asked Questions

What is UUID version 4?

UUID version 4 (UUIDv4) is defined in RFC-4122 and uses random or pseudo-random numbers for generation. It contains 122 bits of randomness with 6 bits reserved for version (4) and variant information. It's the most commonly used UUID version.

What are the different UUID versions?

There are 5 main UUID versions: v1 (time-based with MAC address), v2 (DCE Security), v3 (MD5 hash), v4 (random), and v5 (SHA-1 hash). Version 4 is the most popular for general use. Version 7 is a newer time-ordered UUID gaining adoption.

How can I identify a UUID v4?

UUID v4 can be identified by the version digit in position 13 (after the second hyphen). For v4, this digit is always '4'. The format is: xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx where y is 8, 9, a, or b.

Should I use UUID v4 or v7?

Use UUID v4 for general purposes where ordering doesn't matter - it's universally supported and provides excellent randomness. Use UUID v7 when you need time-ordered UUIDs, better database indexing performance, or chronological sorting.

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