UUID Generator
Make random version 4 or time-ordered version 7 UUIDs, up to 500 at once, and check the version, variant and timestamp of any UUID you paste.
Generate
Check a UUID
The UUIDs are made on your device, and what you paste never leaves it: nothing is sent or saved.
Unique IDs, made on your device
A UUID (universally unique identifier, also called a GUID) is a 128-bit number written as 32 hex digits in groups of 8, 4, 4, 4 and 12. Systems use UUIDs to label database rows, files, messages and API objects, because anyone can make one without asking a central server and still not clash with anyone else’s. This tool makes the two versions RFC 9562, the current UUID standard, suggests for new systems, and reads any UUID you paste.
How to use it
- Choose version 4 or version 7, and how many you need, from 1 to 500.
- Pick a format: uppercase, no hyphens, or wrapped in braces, as some Windows tools write GUIDs.
- Press Generate for a new batch. Changing the format only rewrites the same UUIDs.
- Copy them all, or download them as a text file, one per line.
How each version is built
- Version 4: 122 random bits from crypto.getRandomValues. The 13th hex digit is always 4 (the version), and the 17th is 8, 9, a or b (the variant).
- Version 7: the first 48 bits are the time in milliseconds since January 1, 1970 (Unix time), followed by the version digit 7, a 12-bit counter, the variant and 62 random bits. Within one millisecond the counter goes up by one for each UUID, so a batch sorts in the order it was made.
Checking a UUID
Paste any UUID, with or without hyphens, braces or a urn:uuid: prefix. The checker shows its standard form, its version and variant, and for versions 1, 6 and 7, the date and time stored inside it. It recognizes the special Nil and Max UUIDs, and explains what’s wrong with anything that isn’t a UUID. Times are shown in UTC and in your own time zone.
Good to know
- A version 7 UUID shows when it was made. Use version 4 wherever that matters.
- Check your database’s sort order: some sort stored UUIDs in an unusual byte order, which undoes version 7’s time ordering.
- Version 1 UUIDs can contain the network card address of the computer that made them.
- UUIDs are unique, not secret: don’t use one as a password.
- Checking a long list for repeats? Remove Duplicate Lines finds them.
- Nothing is sent or saved: the UUIDs exist only on your screen until you copy them.