$ uuid --gen

uuid generator.

Generate UUIDs v1, v4, or v7 in bulk. 100% client-side.

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0 UUIDs

Click "Generate" to create UUIDs

What is the difference between UUID v1, v4, and v7?

UUID v1 uses timestamp + MAC address (traceable). v4 is random (most common). v7 is time-ordered random, ideal for database primary keys.

Which UUID version should I use?

Use v4 for most applications. Use v7 for database primary keys (better index performance due to sequential ordering). Use v1 only if you need timestamp tracking.

Can UUIDs collide?

v4 has 2^122 possible values — the chance of collision is astronomically low (1 in 5.3 quintillion). For practical purposes, they are unique.

UUID Versions Compared

Version	Method	Random?	Best For
v1	Timestamp + MAC address	Time-based	Legacy systems (leaks MAC!)
v3	MD5 namespace hash	Deterministic	Same input → same UUID
v4	Random	Yes	General purpose, most common
v5	SHA-1 namespace hash	Deterministic	Same input → same UUID (better than v3)
v7	Timestamp + random	Time-ordered	Database primary keys (new!)

Format Breakdown (v4)

xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx
        |    |   |   |
        |    |   |   └─ version (4)
        |    |   └─ variant (8, 9, a, or b)
        |    └─ random
        └─ random

Database tip: UUID v7 is time-ordered, making it ideal for database primary keys — it avoids the random page splits that v4 causes in B-tree indexes.

learn more in our detailed guide.

→ read the guide