UUIDTools.com

UUID Validator & Decoder

Paste a UUID or GUID to check it and see what is inside: version, variant, timestamp and more.

Accepts hyphenated, 32 hex digits, {braces}, urn:uuid:, any case. Try a fresh v7.

Valid 01a1dd99-1cf3-72ce-a8a7-6499308889cd

Version 7 Unix Epoch time-based Sortable by time
01a1dd991cf3 unix_ts_ms
7 ver
2ce rand_a
a8a76499308889cd var + rand_b
Version7 Unix Epoch time-based
VariantRFC 9562 (formerly RFC 4122 / DCE 1.1) (bits 10)
Timestamp (UTC)2026-11-15T05:06:01.587Z
Unix: 1794719161587 ms. Milliseconds.

Version 7 UUIDs start with a 48-bit Unix timestamp in milliseconds followed by random bits, so they sort by creation time.

Formats

Standard (lowercase) 01a1dd99-1cf3-72ce-a8a7-6499308889cd
Uppercase 01A1DD99-1CF3-72CE-A8A7-6499308889CD
Microsoft GUID (braces) {01A1DD99-1CF3-72CE-A8A7-6499308889CD}
URN urn:uuid:01a1dd99-1cf3-72ce-a8a7-6499308889cd
32 hex digits 01a1dd991cf372cea8a76499308889cd
Base64 (RFC byte order) AaHdmRzzcs6op2SZMIiJzQ==
128-bit integer (decimal) 2169682333400186233829696990102456781
.NET Guid.ToByteArray() (hex) 99dda101f31cce72a8a76499308889cd
.NET Guid bytes (Base64) md2hAfMcznKop2SZMIiJzQ==

API: /api/decode/01a1dd99-1cf3-72ce-a8a7-6499308889cd

How to decode a UUID

Every RFC 9562 UUID stores its version in the 13th hex digit and its variant in the top bits of the 17th digit:

xxxxxxxx-xxxx-Mxxx-Nxxx-xxxxxxxxxxxx
             M = version (1-8)   N = variant (8, 9, a, b = RFC 9562)
Version digitMeaningContains a timestamp?
1Gregorian time-basedYes (100 ns since 1582)
2DCE SecurityPartial
3Name-based, MD5No
4RandomNo
5Name-based, SHA-1No
6Reordered Gregorian timeYes (100 ns since 1582)
7Unix Epoch timeYes (ms since 1970)
8CustomOnly if your format has one

Variant digit

BinaryHex digitVariant
0xxx0 - 7Reserved, NCS backward compatibility
10xx8 - bRFC 9562 (the standard variant)
110xc - dReserved, Microsoft backward compatibility
111xe - fReserved for future definition

The decoder never throws on odd input: unknown versions, legacy variants and the special nil (00000000-…) and max (ffffffff-…) UUIDs all produce a readable result.

Learn more in UUID versions explained.