UUID Generator — Version 4, Free and Local
Random identifiers, generated on your own machine.
Runs on your device What you paste is processed by your own browser. It is never sent to a server, and it is not stored anywhere after you leave the page.
Short answer
Version 4 UUIDs can be generated for free in a web browser, one at a time or fifty at once. The values come from the platform's cryptographically secure random number generator rather than from Math.random, and can be output in lower case, upper case, wrapped in braces in the Microsoft style, or as 32 characters with the hyphens removed. Generation happens on the device, so no identifier is ever sent over a network or seen by anyone else.
At a glance
| Accepts | Nothing — this tool generates |
|---|---|
| Produces | UUID v4, one per line |
| Processing | In your browser |
| Price | Free, no limits |
| Account | Not required |
A version 4 UUID is 122 random bits written in a fixed layout. That is enough randomness that collisions are not a practical concern: generating a billion of them per second for a century would still leave the chance of any two matching negligible, which is what makes them safe to mint independently on many machines with no coordination.
The source of the randomness is what separates a usable generator from a dangerous one. These are drawn from the operating system's own CSPRNG through the browser's crypto API — never from Math.random, which is fast, predictable, and completely unsuitable for anything an attacker might try to guess.
How to use it
- 1
Choose how many
One, or up to fifty at a time for seeding a table or a fixture file.
- 2
Choose the format
Lower case with hyphens is the standard. Braces suit Microsoft tooling; hyphen-free suits a column with a tight length limit.
- 3
Generate
The identifiers appear immediately, one per line. Press again for a fresh set.
- 4
Copy them out
Copy the whole list to the clipboard, or download it as a text file.
Frequently asked questions
Are these UUIDs really unique?
In practice, yes. Each carries 122 random bits, so the probability of two ever colliding is far smaller than the probability of the hardware generating them failing. No central registry or coordination is needed.
Where does the randomness come from?
From the operating system's cryptographic random source, reached through the browser's crypto API. Math.random is not used anywhere here — it is predictable and has no place in generating an identifier.
Are the generated UUIDs sent or stored anywhere?
No. They are produced in your tab and exist only there until you copy them. Nothing is logged, and nobody else ever sees the values you generated.
Which version is this?
Version 4, the random one — the variant used by almost everything that needs an identifier with no meaning attached. Versions 1 and 7 encode a timestamp, which makes them sortable but leaks when they were created.
Can I use these as database primary keys?
Yes, and many schemas do. Be aware that fully random keys scatter inserts across the index, which costs write performance on very large tables — a time-ordered identifier is the usual answer where that matters.