UUID Versions

A detailed guide to all UUID versions and their use cases.

Version 4 (Random)

Completely random UUID. Most commonly used version.

Pros

• Simplest implementation
• Cryptographically secure
• Reveals no information
• Most commonly used

Cons

• Not sortable
• DB index fragmentation

Best for: General purpose, security tokens, when ordering doesn't matter

Version 7 (Unix Epoch)

RECOMMENDED

New standard with Unix timestamp. Sortable and database-friendly.

Pros

• Chronologically sortable
• Excellent for DB indexing
• Contains timestamp
• New standard (RFC 9562)

Cons

• Reveals approximate time
• Newer, less support

Best for: Database primary keys, logs, time-ordered events

Version 1 (Time-based)

Generated using timestamp and MAC address. Ideal for distributed systems.

Pros

• Hardware-level uniqueness
• Contains timestamp

Cons

• Reveals MAC address
• Privacy concern
• Not for security

Version 3 (MD5 Hash) & Version 5 (SHA-1 Hash)

Hash-based versions - generate deterministic UUID from namespace and name. V3 uses MD5, V5 uses SHA-1 (more secure).

Usage Example


                                namespace: "6ba7b810-9dad-11d1-80b4-00c04fd430c8" (DNS)

                                name: "example.com"

                                → UUID v5: "cfbff0d1-9375-5685-968c-48ce8b15ae17"

Best for: When you need the same UUID for the same input (idempotency)

Version Comparison

Version	Source	Sortable	Secure	Use Case
v1	Time + MAC	~	✗	Distributed systems
v3	MD5 hash	✗	~	Deterministic IDs
v4	Random	✗	✓	General purpose
v5	SHA-1 hash	✗	✓	Deterministic IDs
v7	Unix time + random	✓	✓	DB primary keys

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