Are these UUIDs guaranteed to be unique?

Not mathematically guaranteed, but practically yes. A version-4 UUID has 122 random bits, so the chance of any two ever colliding is astronomically small — you'd need to generate billions of UUIDs per second for centuries before a collision became likely.

What's the difference between UUID and GUID?

They're the same concept — GUID (Globally Unique Identifier) is Microsoft's name for what the rest of the industry calls a UUID. This tool generates standard RFC 4122 version-4 UUIDs, which are interchangeable with GUIDs in format.

UUID Generator

Generate random version-4 UUIDs for use in code and databases.

How this is calculated

16 random bytes with version and variant bits set per RFC 4122

Assumptions used in this calculation

UUID version: Generates version-4 (random) UUIDs using cryptographically secure random bytes, not time-based (v1) or name-based (v3/v5) UUIDs.

About this calculator

The UUID generator creates RFC 4122-compliant version-4 (random) UUIDs using your browser's Web Crypto API, entirely client-side.

Worked example

5 UUIDs

Result: 5 random UUIDs

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About this calculator

Frequently asked questions

Are these UUIDs guaranteed to be unique?

What's the difference between UUID and GUID?

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