UUID v4 (Universally Unique Identifier version 4) is a 128-bit randomly generated identifier formatted as 8-4-4-4-12 hexadecimal characters. The "v4" means it is randomly generated, as opposed to v1 (time-based) or v5 (name-based).

Are UUID collisions possible?

Theoretically yes, but practically no. UUID v4 has 2^122 possible values. The probability of generating a duplicate among 1 billion UUIDs is about 1 in 800 million billion — effectively impossible for any real-world use case.

What is the difference between UUID and GUID?

They are the same thing. GUID (Globally Unique Identifier) is Microsofts term for UUID. Both refer to the same 128-bit identifier format, just with different names from different ecosystems.

Can I use UUIDs as database primary keys?

Yes — UUIDs are widely used as primary keys, especially in distributed systems where you need to generate IDs without a central sequence. The tradeoff versus auto-increment integers is slightly larger storage (16 bytes vs 4-8 bytes) and non-sequential ordering.

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UUID Generator

Generate one or hundreds of UUID v4s instantly. Bulk generation, one-click copy all, uppercase/lowercase options. Free UUID generator — no sign-up.

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About This Tool

Generate cryptographically random UUID v4 identifiers instantly. Generate up to 100 at once, copy individually or all at once, and toggle between uppercase and lowercase formats.