UUIDs provide collision-resistant identifiers for distributed systems.
UUID versions
- v1: Timestamp-based (reveals MAC address and creation time).
- v4: Random (most common, cryptographically random).
- v5: Name-based with SHA-1 hashing (deterministic).
- v7: New timestamp-based with improved sorting (RFC draft).
Format
- 8-4-4-4-12 hexadecimal digits: 550e8400-e29b-41d4-a716-446655440000.
Use cases
- Database primary keys in distributed systems.
- Session identifiers and API tokens.
- File and document naming.
- Correlation IDs in microservices.
Security considerations
- UUIDv1 leaks MAC address and timestamp.
- Prefer UUIDv4 for security-sensitive applications.
- Not suitable as secrets or passwords.
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