Question 1

What is UUID v1?

Accepted Answer

UUID v1 is a timestamp-based universally unique identifier defined in RFC 4122. It combines a Gregorian timestamp with a MAC address, making UUIDs sortable by creation time. However, it has privacy concerns due to the embedded MAC address and is considered legacy. Modern alternatives like UUID v6 and v7 are recommended.

Question 2

Should I use UUID v1?

Accepted Answer

Generally, no. UUID v1 is a legacy standard with privacy concerns because it includes your MAC address. For new projects, use UUID v6 or v7 for time-ordered identifiers (they're more efficient and private) or UUID v4 for random identifiers. Only use v1 if you need compatibility with existing v1-based systems.

Question 3

What's the difference between UUID v1 and v6?

Accepted Answer

UUID v6 is a modern replacement for v1. Both are timestamp-based, but v6 reorders the timestamp bits for better lexicographic sorting, resulting in superior database performance. V6 maintains compatibility with v1 systems while providing better indexing. If you're using v1, consider migrating to v6.

Question 4

Does UUID v1 expose my MAC address?

Accepted Answer

Yes, UUID v1 traditionally includes the network card's MAC address in the node field (last 48 bits). This can be a privacy concern as it reveals hardware information. Some implementations use random node values instead, but this defeats the purpose. Use UUID v4 for privacy or v6/v7 for time-ordering without MAC addresses.

Version	Time-based	Sortable	Best Use Case
v1			Legacy systems
v4			Random IDs, security
v6			Modern databases
v7			Latest standard (2024)

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