Random UUID
|v4
f78a91df-486d-4adc-b544-feddb7902455
Time based UUID
|v6
1f181dc3-c66e-6300-a623-64e721d2d327
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.
019f7014-b530-76db-96c4-fce058d87d8d
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).
1f181dc3-c66e-6301-a9ef-2046fcbf55ef
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.
9e4ea223-5d6a-4c6c-be46-b5c60998cdac
UUID v1
|Time-based + MAC Address
High uniqueness, sortable by time. Privacy concern due to including the generating machine's MAC address.
3c66e302-81dc-11f1-a623-65e721d2d327