UUID version 1 is a time-based identifier built from the current timestamp and a node identifier (historically the machine’s MAC address). It was one of the original UUID schemes and guarantees uniqueness through the combination of time and hardware.
This generator creates v1 UUIDs in your browser. Use it when you need time-based identifiers or want to experiment with the classic time-based format.
How UUID v1 works
A v1 UUID encodes a 60-bit timestamp counting 100-nanosecond intervals since 1582, a clock sequence to handle clock changes, and a node identifier. Together these make collisions extremely unlikely as long as the node value is unique.
Because the timestamp is embedded, v1 UUIDs are loosely ordered by creation time, although the byte layout means they do not sort lexicographically the way v7 does.
When to use v1 (and when not to)
Use v1 when you specifically need a time-based identifier compatible with older systems. However, classic v1 can leak the generating machine’s MAC address and creation time, which is a privacy concern.
For new applications that want time ordering, UUID v7 is usually the better choice: it is sortable, standardised in RFC 9562, and does not expose hardware identifiers.
Frequently asked questions
- Does UUID v1 expose my MAC address?
- Traditional v1 implementations embed the node’s MAC address. Many modern libraries instead use a random node value to avoid leaking hardware information.
- Is UUID v1 sortable?
- It is time-based but not lexicographically sortable because of how the timestamp bytes are arranged. Use UUID v7 if you need IDs that sort by creation time.
- What is the difference between UUID v1 and v7?
- Both are time-based, but v7 places the timestamp in the most significant bits for clean sorting and uses random data instead of a MAC address, making it more private and database-friendly.