UUID Generator
Inspect a UUID
About this tool
A UUID (also called a GUID) is a 128-bit identifier written as 32 hex digits, such as 3f2b8c1e-5d4a-4c7b-9e1a-2b6f0a8d7c34.
Use it for database keys, request IDs, file names and anything that needs a unique ID without asking a central server.
Everything runs in your browser. The identifiers are generated locally and never sent anywhere.
How it works
- Version 4 is 122 random bits from
crypto.getRandomValues(), with the version and variant bits set as RFC 9562 (the update of RFC 4122) requires. It is the usual choice. - Version 7 starts with the current time in milliseconds, followed by a counter and random bits. IDs created later sort after earlier ones, which keeps database indexes compact and makes them roughly sortable by creation time. IDs created in the same millisecond keep their order through the counter. The creation time is readable from the ID, so do not use it where that would leak information.
- Nil is all zeros, sometimes used as a placeholder.
- The format options only change how the same ID is written. The .NET and Windows style is uppercase with braces; many databases store the form without hyphens.
- You can create up to 1,000 at once. Larger numbers are rounded down to 1,000.
- The inspector reads the version and variant of any UUID, and the embedded time for versions 1 and 7.
FAQ
Q. Can two UUIDs collide?
A. For random version 4 IDs it is possible in theory but, with 122 random bits, the chance is negligible in practice. Uniqueness is probabilistic, not guaranteed.
Q. Is a UUID safe to use as a secret token?
A. Version 4 from this page is unpredictable, but a UUID is meant as an identifier. For session tokens and API keys, use a longer random value and treat it as a secret. Never use version 7 for secrets, because it contains the time.