UUIDTools.com

Version 6 UUID Generator

Like v1, but reordered so it sorts by time. For v1 migrations.

Decode
Options & format

Formatting is applied instantly in your browser. A GUID is a UUID: tick Uppercase + Braces for the Microsoft registry style.

API
http://uuidtools.com/api/generate/v6

Plain-text and JSON API docs: no key required.

About Version 6 UUIDs

A version 6 UUID is a version 1 UUID with its timestamp fields reordered so the most significant bits come first. The result sorts by creation time while staying structurally compatible with v1.

It exists mainly so systems that already produce v1 can migrate without changing the timestamp source. For greenfield projects RFC 9562 recommends v7.

Structure

time_high (32) | time_mid (16) | 6 + time_low (16) | variant + clock_seq (16) | node (48)

When to use it

  • Migrating from v1 while gaining time-ordering.

When to avoid it

  • New systems without a v1 legacy: v7 is simpler and uses a Unix timestamp.

Frequently asked questions

What is the difference between v1 and v6?

Same data, different byte order. v6 puts the high timestamp bits first so lexicographic order equals chronological order.