UUID Generator
Generate one or more UUID v4 values instantly. Pick how many you need (up to 20), choose the format (standard, uppercase, or without hyphens), and copy them all at once. Useful for seeding databases, testing, or anywhere you need unique IDs.
How to use
- Set how many UUIDs you need - anywhere from 1 to 20.
- Pick the format: standard lowercase with hyphens, all uppercase, or compact with no hyphens.
- Click Generate, then copy individual UUIDs or copy all of them at once.
Related tools:
A UUID (Universally Unique Identifier) is a 128-bit identifier written as 32 hexadecimal characters in 5 groups separated by hyphens: xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx. UUID v4 is randomly generated. The probability of two v4 UUIDs colliding is astronomically low - generating 1 billion UUIDs per second for 100 years would give a 50% chance of a single collision.
UUIDs are used as primary keys in databases (avoids needing a sequential ID from the database, enables distributed inserts without coordination), as unique identifiers for API resources, session tokens, and request tracing. The generator here produces multiple UUIDs at once in standard, uppercase, or no-hyphen format.
Frequently Asked Questions
What is the difference between UUID v1, v3, v4, and v5?
v1 is time-based (encodes the current timestamp and MAC address). v3 and v5 are name-based using MD5 and SHA-1 hashing respectively - same input always produces the same UUID. v4 is random. v4 is by far the most commonly used for its simplicity and privacy (no embedded timestamps or MAC addresses).
Are UUIDs truly unique?
Practically yes. A v4 UUID is 122 bits of randomness. The chance of any two random UUIDs matching is roughly 1 in 5.3 x 10^36. For all practical engineering purposes, UUIDs are unique.
Should I use UUID or auto-increment integers for database primary keys?
Auto-increment is simpler and slightly faster for single-server databases. UUIDs work better for distributed systems (no coordination needed), when you need to generate IDs before inserting to the database, or when you want to avoid predictable sequential IDs for security reasons.