How to use
- Choose how many identifiers.
- Pick upper case or the presence of hyphens.
- Copy one identifier or copy them all.
What is a version 4 UUID?
It is the version based on random numbers. It has 32 hexadecimal digits in five groups separated by hyphens, with a 4 always at the start of the third group. The chance of two identical identifiers is so small that it is ignored in practice.
When is it useful?
It helps create keys that do not collide without a central authority handing out numbers, as in distributed systems and offline-capable apps, and in uploaded file names to avoid duplicates.
Frequently asked questions
Are the identifiers securely random?
Yes. They are generated with the browser's cryptographic random interface.
Can a UUID repeat?
In theory yes, but the probability is so tiny that a repeat has not been observed in practice.
Are identifiers saved?
No. They are generated on your device and vanish when you close the page.