UUID Validator & Decoder: Version, Variant, Timestamp

Valid 01a18d5f-ff29-729a-a7f2-f25c2413dbcb

Version 7 Unix Epoch time-based Sortable by time

01a18d5fff29 unix_ts_ms

7 ver

29a rand_a

a7f2f25c2413dbcb var + rand_b

Version	7 Unix Epoch time-based
Variant	RFC 9562 (formerly RFC 4122 / DCE 1.1) (bits `10`)
Timestamp (UTC)	`2026-10-30T15:14:01.129Z` Unix: 1793373241129 ms. Milliseconds.

Version

7 Unix Epoch time-based

Variant

RFC 9562 (formerly RFC 4122 / DCE 1.1) (bits 10)

Timestamp (UTC)

2026-10-30T15:14:01.129Z
Unix: 1793373241129 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)	`01a18d5f-ff29-729a-a7f2-f25c2413dbcb`
Uppercase	`01A18D5F-FF29-729A-A7F2-F25C2413DBCB`
Microsoft GUID (braces)	`{01A18D5F-FF29-729A-A7F2-F25C2413DBCB}`
URN	`urn:uuid:01a18d5f-ff29-729a-a7f2-f25c2413dbcb`
32 hex digits	`01a18d5fff29729aa7f2f25c2413dbcb`
Base64 (RFC byte order)	`AaGNX/8pcpqn8vJcJBPbyw==`
128-bit integer (decimal)	`2168055215407361527465893356452961227`
.NET Guid.ToByteArray() (hex)	`5f8da10129ff9a72a7f2f25c2413dbcb`
.NET Guid bytes (Base64)	`X42hASn/mnKn8vJcJBPbyw==`

Standard (lowercase)

01a18d5f-ff29-729a-a7f2-f25c2413dbcb

Uppercase

01A18D5F-FF29-729A-A7F2-F25C2413DBCB

Microsoft GUID (braces)

{01A18D5F-FF29-729A-A7F2-F25C2413DBCB}

URN

urn:uuid:01a18d5f-ff29-729a-a7f2-f25c2413dbcb

32 hex digits

01a18d5fff29729aa7f2f25c2413dbcb

Base64 (RFC byte order)

AaGNX/8pcpqn8vJcJBPbyw==

128-bit integer (decimal)

2168055215407361527465893356452961227

.NET Guid.ToByteArray() (hex)

5f8da10129ff9a72a7f2f25c2413dbcb

.NET Guid bytes (Base64)

X42hASn/mnKn8vJcJBPbyw==

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 digit	Meaning	Contains a timestamp?
1	Gregorian time-based	Yes (100 ns since 1582)
2	DCE Security	Partial
3	Name-based, MD5	No
4	Random	No
5	Name-based, SHA-1	No
6	Reordered Gregorian time	Yes (100 ns since 1582)
7	Unix Epoch time	Yes (ms since 1970)
8	Custom	Only if your format has one

Variant digit

Binary	Hex digit	Variant
`0xxx`	0 - 7	Reserved, NCS backward compatibility
`10xx`	8 - b	RFC 9562 (the standard variant)
`110x`	c - d	Reserved, Microsoft backward compatibility
`111x`	e - f	Reserved 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.

UUID Validator & Decoder

Valid 01a18d5f-ff29-729a-a7f2-f25c2413dbcb Copy

Formats

How to decode a UUID

Variant digit

Valid `01a18d5f-ff29-729a-a7f2-f25c2413dbcb`