RFC 9562
UUID v7 generator
UUID version 7 keeps a Unix millisecond timestamp in the high bits and uses random bits after the version and variant. This page defaults to v7 and can still make a v4.
Generate UUIDs
Choose a version and a count, then generate.
The canonical text looks like xxxxxxxx-xxxx-7xxx-yxxx-xxxxxxxxxxxx. The character y is 8, 9, a, or b. Those are the RFC variant.
Across different milliseconds, the text sorts by time because the timestamp comes first and the hyphens stay in fixed positions. Inside one millisecond the rest is random, so this page does not produce a counter.
Where the bits go
- Bits 0–47: Unix time in milliseconds.
- Bits 48–51: version 7.
- Bits 52–63: rand_a, random on this page.
- Bits 64–65: variant 10.
- Bits 66–127: rand_b, random.
Questions
What is the layout of UUID v7?
RFC 9562 puts a 48-bit big-endian Unix timestamp in milliseconds in the first bits, sets the version to 7, then 12 random bits, the variant bits 10, and 62 more random bits.
Which clock is encoded?
The clock is Date.now() in this browser: milliseconds since 1970-01-01 UTC, excluding leap seconds. A wrong computer clock writes a wrong timestamp.
Is this the same as a database uuidv7()?
The version, variant, and millisecond field follow RFC 9562. PostgreSQL 18 also stores a sub-millisecond fraction in the 12-bit rand_a field and keeps order inside one backend. This page leaves those 12 bits random.