Random UUID
|v4
2404e393-3272-4cd7-bac2-cce6ed7c3a36
Time based UUID
|v6
1f181e61-784d-6b00-a0ce-8ad0b2e12e43
UUID v7
|Time + Random
Uses a 48-bit Unix epoch timestamp (millisecond precision) followed by random bits. Time-sortable and optimized for better database indexing than V1. Considered the modern best practice.
019f7055-4cb0-7628-b877-9a6fe9519f2d
UUID v6
|Reordered Time-based
Time-based like V1 but reorders the bits to be monotonically increasing (better for database indexing). Does not expose the MAC address (often uses a random node ID instead).
1f181e61-784d-6b01-acf6-87dff97d2b03
UUID v4
|Random (Pseudo-random numbers)
Maximum unpredictability and privacy. Not sortable by time. Higher (but still very low) theoretical collision chance compared to time-based.
819037aa-c10d-4ce8-b223-c5cbe96d5fce
UUID v1
|Time-based + MAC Address
High uniqueness, sortable by time. Privacy concern due to including the generating machine's MAC address.
1784db02-81e6-11f1-a0ce-8bd0b2e12e43