Random UUID
|v4
8307a998-f4ad-43de-88c8-8bfeeaa27430
Time based UUID
|v6
1f1377b1-bcbc-6440-bc2f-116569154578
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.
019d88a0-c684-7009-85c4-c47299ddb297
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).
1f1377b1-bcbc-6441-a729-5fb91aee5cf1
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.
da35e486-4057-42d7-a512-f75b52f9ea52
UUID v1
|Time-based + MAC Address
High uniqueness, sortable by time. Privacy concern due to including the generating machine's MAC address.
1bcbc442-377b-11f1-bc2f-116569154578