UUID v1 Generator

UUID v1 is a time-based identifier:

xxxxxxxx-xxxx-1xxx-xxxx-xxxxxxxxxxxx

The 1 in the third group indicates version 1.

• Timestamp: 60 bits, representing 100-nanosecond intervals since 15 October 1582 (UTC)
• Clock sequence: 14 bits, for uniqueness if timestamp goes backward
• Node identifier: 48 bits, typically the MAC address of the generating machine

A typical UUID v1:

550e8400-e29b-11d4-a716-446655440000

• 550e8400-e29b-1 = timestamp
• 1 = version (v1)
• 1d4-a716 = clock sequence
• 446655440000 = node identifier

1. Click "Generate" to create a new UUID v1
2. Copy the result
3. Repeat for multiple UUIDs

• Monotonically increasing: UUIDs generated at different times sort chronologically
• Universally unique: MAC address + timestamp makes collisions extremely unlikely
• No coordination needed: Each machine generates independently

• Privacy concern: MAC address is included (though modern implementations randomize)
• Predictable: If you know when and where it was generated, you can predict others
• Not cryptographically secure: Not suitable for security tokens

• Database primary keys
• Log file entries
• Transaction IDs
• Event tracking
• Replication identifiers

Is UUID v1 sequential? Yes, within a single machine, v1 UUIDs are monotonically increasing.

Can two machines generate the same UUID? Extremely unlikely. The MAC address space is huge, and timestamps are precise.

What about privacy? Modern implementations often use random node identifiers instead of MAC addresses.

How is the timestamp encoded? As 100-nanosecond intervals since 15 October 1582 (the Unix epoch is 369 days later).

Can I decode a v1 UUID? Yes, the timestamp and node can be extracted, revealing when and where it was generated.

Should I use v1 or v4? Use v1 for chronological sorting, v4 for privacy and unpredictability.