Where is the version stored in a UUID?

The version is the first hex digit of the third group — the 13th hex character overall, position 9 counting from 0 ignoring hyphens. A standard UUID looks like xxxxxxxx-xxxx-Mxxx-Nxxx-xxxxxxxxxxxx, where M is the version digit and N encodes the variant.

What are the UUID versions?

Version 1 is time-and-MAC based, version 2 is DCE security, versions 3 and 5 are name-based (MD5 and SHA-1), version 4 is random, and version 7 is a newer time-ordered random UUID from RFC 9562. The tool names each one it detects.

What is the variant field?

The variant indicates the layout of the UUID. The most significant bits of the 17th hex digit determine it: 10x is the standard RFC 4122 variant, 0xx is the legacy NCS variant, and 110 is the Microsoft GUID variant.

Does it validate the format?

Yes. It checks that the input is 32 hexadecimal digits arranged in the 8-4-4-4-12 pattern. Invalid lengths or non-hex characters are rejected with an explanation before any version is reported.

UUID Version Identifier

Every RFC 4122 / RFC 9562 UUID carries its own version and variant inside its bits. This tool parses a UUID string, validates its shape, and tells you exactly which version generated it and which variant layout it uses.

How it works

A canonical UUID has 32 hex digits grouped 8-4-4-4-12:

xxxxxxxx-xxxx-Mxxx-Nxxx-xxxxxxxxxxxx
              │      │
              │      └─ variant bits (top of this nibble)
              └─ version digit (1,2,3,4,5,7…)

The version is simply the value of the M nibble. The variant is read from the high bits of the N nibble: a leading 10 means the standard RFC 4122 variant, 0 means the legacy NCS variant, and 110 means the Microsoft GUID variant. The tool strips hyphens and braces, lower-cases the input, and confirms it is 32 hex digits before reading these fields.

Example and tips

f47ac10b-58cc-4372-a567-0e02b2c3d479 reports as version 4 (random), RFC 4122 variant, because the 13th digit is 4 and the 17th (a) starts with binary 10. A version 7 UUID like 018f... is time-ordered, making it sortable by creation time — increasingly preferred over version 4 for database keys.