What is a Universally Unique Identifier (UUID)?
A UUID is a 128-bit identifier standardized by the Internet Engineering Task Force (IETF) in RFC 9562 (which supersedes the legacy RFC 4122). In canonical textual representation, a UUID consists of 32 hexadecimal digits displayed in 5 hyphen-separated groups (8-4-4-4-12), yielding a 36-character string such as f47ac10b-58cc-4372-a567-0e02b2c3d479.
UUID v4 vs. UUID v7: Key Differences
| Specification | UUID v4 (Random) | UUID v7 (Time-Ordered) |
|---|---|---|
| Primary Component | 122 bits of cryptographic pseudo-randomness | 48-bit Unix timestamp (milliseconds) + 74 random bits |
| Database Indexing | Scattered insertions; can fragment B-Trees at high scale | Naturally sequential; optimizes B-Tree locality and cache efficiency |
| Version Nibble | 0100 (Digit 4 at position 13) |
0111 (Digit 7 at position 13) |
| Standard Reference | RFC 9562 Section 5.4 | RFC 9562 Section 5.7 |
Security and Client-Side Privacy
This generator runs exclusively client-side in your web browser via the W3C Web Cryptography API (crypto.randomUUID and crypto.getRandomValues). Identifiers are generated in memory without network requests, logs, or external telemetry.
Security note: While UUID v4 provides cryptographically strong pseudo-random bits, UUIDs should be treated as unique object identifiers rather than cryptographic secrets, password hashes, or authentication tokens.