UUID Generator
Generate random UUID v4 identifiers. Bulk generation up to 100, with options for uppercase and with or without hyphens
1-100 UUIDs
What's a UUID?
Universally Unique Identifier - a 128-bit ID with a standard format: 8-4-4-4-12 hex digits separated by hyphens. Example: 550e8400-e29b-41d4-a716-446655440000. Designed so that any system can generate UUIDs independently and the chance of collision is essentially zero (~10^-18 collision probability per generation, less likely than a particular star colliding with Earth).
Common uses: database primary keys (especially in distributed systems), API identifiers, session tokens, file names. Most languages have built-in UUID generation: JavaScript crypto.randomUUID(), Python uuid.uuid4(), Java UUID.randomUUID(). Different versions of UUID exist - v4 (random) is most common, v7 (time-ordered random) is increasingly popular for database keys.
UUID Versions
| Version | Description |
|---|---|
| v1 | Time + MAC address (privacy concern) |
| v3 | MD5 hash of namespace + name |
| v4 | Random (most common) |
| v5 | SHA-1 hash of namespace + name |
| v6 | Time-ordered (better for indexes) |
| v7 | Unix timestamp + random (newest) |
| NIL | All zeros: 00000000-0000-0000-0000-000000000000 |
Frequently Asked Questions
Why use UUID instead of incrementing IDs?
Distributed systems can generate IDs independently without coordinating with a central counter. Better for microservices, sharded databases, mobile apps generating IDs offline. Trade-off: UUIDs are larger (16 bytes vs 4 for integer), and v4 random UUIDs hurt database index performance vs sequential IDs.
Should I use v4 or v7?
v7 is newer (RFC 9562, 2024) and ordered by time, which keeps database indexes fast. v4 is well-supported everywhere but causes random insertion in indexes. New projects in databases supporting v7 (most modern ones) should consider v7 for better performance.
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