How uuid validator works
A UUID (Universally Unique Identifier), also called a GUID, is a 128-bit identifier usually written as eight groups of hex digits separated by hyphens: 8-4-4-4-12 (36 characters total). This validator checks that your string matches that shape after accepting hyphenated, compact (32 hex), urn:uuid:, and braced {…} input forms.
The version of a UUID is stored in the high nibble of the 13th hex digit (the first digit of the third group): 1 for time-based, 3 for name-based MD5, 4 for random, 5 for name-based SHA-1, 6 for reordered time, 7 for Unix-epoch time, and 8 for vendor-defined. The variant is stored in the high bits of the 17th hex digit (the first digit of the fourth group); RFC 4122 uses the 10xx pattern.
The validator returns the canonical lowercase hyphenated form, the detected version and its name, the variant, and flags for the special nil UUID (all zeros) and max UUID (all f’s). Everything runs in your browser; nothing is uploaded.
Frequently asked questions
How does it tell the UUID version?
The version is the first hex digit of the third group. For example, in 550e8400-e29b-41d4-a716-446655440000 that digit is 4, so it is a version 4 (random) UUID. The validator reports both the number and a plain-English name.
What UUID formats does it accept?
It accepts the standard hyphenated form, a compact 32-character hex string with no hyphens, the urn:uuid: prefix, and a braced {…} form. All are normalized to the canonical lowercase hyphenated form in the result.
What is the nil UUID?
The nil UUID is 00000000-0000-0000-0000-000000000000 — all 128 bits zero. It is a reserved special value used to represent "no UUID". The max UUID is the opposite: every bit set to one.
Does validating a UUID guarantee it is unique?
No. Validation only checks that the format, version and variant bits are well-formed. It does not check that the UUID has never been issued. Uniqueness comes from the generation algorithm, not from the shape.
