What's the difference between v4 and v7?

v4 is 122 random bits — the common default, with nothing predictable in it. v7 starts with the current time in milliseconds, so UUIDs sort in the order they were created, which keeps database indexes fast. UUIDs made in the same millisecond are numbered so a batch still sorts correctly.

Can two UUIDs ever be the same?

Not in practice. With 122 random bits in a v4, you would need to generate billions per second for many years before a clash became likely. They come from the browser's secure random generator.

Does a v7 UUID reveal anything?

Yes — it contains its creation time to the millisecond. If that matters, use v4.

Can I use a UUID as a password or secret key?

No. UUIDs are identifiers, not secrets. Use the Password Generator for anything that has to stay private.

Utility

UUID Generator

Generate random (v4) or time-ordered (v7) UUIDs — one or a thousand at a time. Made with your browser's secure random generator.

Options

Version

How many

UppercaseHyphensBraces { }

0 UUIDs

How it works

1
Choose version 4 (random) or version 7 (time-ordered).
2
Set how many you need (up to 1,000) and any formatting — uppercase, no hyphens, braces.
3
Copy them all, or download a .txt file. Press Generate new for a fresh set.

UUID Generator — frequently asked questions

What's the difference between v4 and v7?: v4 is 122 random bits — the common default, with nothing predictable in it. v7 starts with the current time in milliseconds, so UUIDs sort in the order they were created, which keeps database indexes fast. UUIDs made in the same millisecond are numbered so a batch still sorts correctly.
Can two UUIDs ever be the same?: Not in practice. With 122 random bits in a v4, you would need to generate billions per second for many years before a clash became likely. They come from the browser's secure random generator.
Does a v7 UUID reveal anything?: Yes — it contains its creation time to the millisecond. If that matters, use v4.
Can I use a UUID as a password or secret key?: No. UUIDs are identifiers, not secrets. Use the Password Generator for anything that has to stay private.