v4 (Random)
v7 (Timestamp)
Click "Generate" to create UUIDs
UUID to Validate
About UUIDs
A Universally Unique Identifier (UUID) is a 128-bit identifier standardized in RFC 9562. UUIDs are formatted as 36 characters in the pattern 8-4-4-4-12 (e.g., 550e8400-e29b-41d4-a716-446655440000) and are designed to be globally unique without a central authority.
What is a UUID?
- 128-bit identifier - large enough to be globally unique
- 36 characters - 32 hex digits plus 4 hyphens in 8-4-4-4-12 format
- No central authority - any system can generate UUIDs independently
- Multiple versions - different generation strategies for different use cases
UUID Versions Compared
| Version | Based On | Key Property |
|---|---|---|
v1 | Timestamp + MAC address | Time-based, leaks hardware identity |
v4 | Random number generator | No information leakage, most widely used |
v5 | SHA-1 hash of namespace + name | Deterministic - same input always gives same UUID |
v7 | Unix timestamp + random | Time-sortable, ideal for database primary keys |
When to Use Each Version
- v4 (random) - general-purpose unique IDs, session tokens, correlation IDs
- v7 (timestamp-sortable) - database primary keys where insertion order matters, event IDs
- v5 (name-based) - deterministic IDs derived from a name (e.g., generating a UUID from a URL)