Developer · Validator
UUID validator.
Check a UUID's format, decode its version and variant, and read the timestamp inside v1, v6 and v7 UUIDs. Runs in your browser; nothing is sent anywhere.
Input
Result
Enter a UUID and press Check.
How a UUID is read
A UUID is 128 bits, written as 32 hex digits in the groups 8-4-4-4-12. This page checks that shape, then reads two fixed fields defined in RFC 9562.
Variant: the top bits of the first byte of the fourth group. 10xx (hex 8, 9, a, b) is the variant RFC 9562 defines. 0xxx is reserved for legacy NCS UUIDs and includes the Nil UUID, 110x (c, d) is reserved for Microsoft compatibility, and 111x (e, f) is reserved for future use and includes the Max UUID.
Version: the first hex digit of the third group, only meaningful when the variant is 10xx. RFC 9562 lists 1 (Gregorian time), 2 (DCE Security, reserved), 3 (MD5 name-based), 4 (random), 5 (SHA-1 name-based), 6 (reordered Gregorian time), 7 (Unix Epoch time) and 8 (custom). 0 is unused and 9 to 15 are reserved.
Timestamps: v1 and v6 store a 60-bit count of 100 nanosecond intervals since 1582-10-15 00:00:00 UTC; the two versions differ only in byte order (v6 puts the most significant bits first so it sorts by time). v7 stores a 48-bit count of Unix milliseconds in its first 12 hex digits. The RFC's own v1 and v6 examples both decode to 2022-02-22 19:22:22 UTC, and its v7 example to 1645557742000 ms.
Nil and Max: 00000000-0000-0000-0000-000000000000 (all bits 0) and ffffffff-ffff-ffff-ffff-ffffffffffff (all bits 1) are special sentinel values, not versioned UUIDs.
Sources: RFC 9562, Universally Unique IDentifiers (UUIDs): section 4 (format), 4.1 Table 1 (variants), 4.2 Table 2 (versions), 5.9 and 5.10 (Nil and Max) and Appendix A (test vectors and the 122192928000000000 Gregorian-to-Unix offset). The embedded time is whatever the generator wrote; nothing guarantees it is accurate.
Frequently asked questions
Does a valid result mean this UUID exists?
No. It only means the text is well-formed. Nothing here can tell you whether a UUID was ever generated, assigned or used.
Why is the Nil UUID shown as "valid" but with no version?
Its bits are all zero, which places it in the reserved NCS variant, so the version field is not defined for it. RFC 9562 specifies it as a special value.
Why does my UUID have no timestamp?
Only versions 1, 6 and 7 embed a time. Versions 3 and 5 are hashes of a name, 4 is random, and 8 is custom, so nothing can be decoded reliably.
What about GUIDs from Microsoft tools?
They use the same 128 bits and often the same text form, sometimes in braces, which this page accepts. Some older ones fall in the Microsoft variant (110x), which is reported as reserved.
Format check only
This tool checks the structure of a UUID string and decodes fields from RFC 9562. It cannot confirm the UUID was issued or belongs to anything. Nothing you type is stored or sent anywhere.