UUID Generator
Generate a version 4 UUID, the identifier format most commonly used in software development.
How to use the UUID Generator
- Press Generate UUID. A 36-character version 4 value appears in the display.
- Press Copy result to put the value now on screen onto the clipboard.
- Press the button again for more; each value is added to the history below.
- Press Clear history to empty that list and the stored copy of it.
What the 36 characters are made of
The value follows the 8-4-4-4-12 pattern, filled with hexadecimal digits. Two positions are fixed: the third group starts with 4 for version 4, and the fourth group starts with 8, 9, a or b for the variant. Of the 128 bits, 122 are random.
| Group | Length | Content |
|---|---|---|
| 1st | 8 | random hex |
| 3rd | 4 | version digit 4, then 3 random |
| 4th | 4 | variant digit 8, 9, a or b, then 3 random |
| 5th | 12 | random hex |
The 2nd group is 4 random hex digits. Hyphens are separators only.
Where these values are fine and where they are not
The digits come from the browser's ordinary random function, not a cryptographic one. That suits row keys, test data and trace identifiers. For session tokens or secret links, use crypto.randomUUID or another cryptographic source.
Frequently asked questions
What is a UUID?
A 128-bit identifier designed so that separately generated values will not collide, even across different systems with no coordination between them.
Can I use it as a database key?
Yes. Version 4 UUIDs are supported by virtually every database. Note that random UUIDs can fragment index performance on very large tables compared with sequential keys.
Is the history sent anywhere?
No. The list is written to this browser's local storage, up to fifty entries, and stays on this device. Clear history removes both the list and the stored copy.
Can I generate a batch at once?
No. One press gives one UUID, so for a bulk list press repeatedly and copy the values out of the history.