UUID Version 1 (Gregorian time + node)

UUIDv1 is a 128-bit time-based UUID: a 60-bit timestamp counting 100-nanosecond intervals since 1582-10-15 00:00:00 UTC (the Gregorian calendar epoch), a 14-bit clock sequence, and a 48-bit node identifier (historically the host MAC address). The time field is split across three sections, so v1 strings are NOT lexicographically time-sortable; UUIDv6 reorders the same data to fix that.

identifier

spec: RFC 9562 §5.1

length 128 bits not sortable hex with dashes (8-4-4-4-12)

example:

c232ab00-9414-11ec-b3c8-9f6bdeced846

field	bits	meaning
time_low	32	Low 32 bits of the 60-bit Gregorian timestamp (100-ns intervals since 1582-10-15).
time_mid	16	Middle 16 bits of the timestamp.
ver	4	version = 0b0001 (1).
time_high	12	High 12 bits of the timestamp.
var	2	variant = 0b10 (RFC 9562 / former RFC 4122).
clock_seq	14	Clock sequence, to avoid collisions when the clock is set backwards or the node changes.
node	48	Node id; historically the 48-bit IEEE 802 MAC address, may be a random multicast-bit-set value for privacy.

The 60-bit timestamp is scattered (time_low / time_mid / time_high), so byte order does NOT match time order; v1 is not sortable. UUIDv6 (RFC 9562 §5.6) is the field-compatible, time-ordered re-lay-out.
The example c232ab00-9414-11ec-b3c8-9f6bdeced846 is the RFC 9562 Appendix worked example; the version nibble (13th hex char) is '1' and the variant nibble begins '10' (here 'b').
Embedding the MAC address leaks the host; RFC 9562 permits a random node id with the multicast bit set instead.

agent: curl -H 'accept: application/json' wire.phall.io/identifier/uuidv1 or /identifier/uuidv1.json

UUID Version 1 (Gregorian time + node)

identifier

provenance

see also