About UUID Generator
UUID Generator produces version 4 universally unique identifiers from the browser cryptographic random source. Each identifier is 128 bits of randomness presented in the standard eight-four-four-four-twelve hexadecimal grouping, and any number from one to a hundred can be generated at once, one per line.
Version 4 identifiers carry no information at all — no timestamp, no machine identifier, no sequence — which is precisely their advantage for anything that will be exposed. Because they cannot be ordered or predicted, an identifier that leaks reveals nothing about when it was created or how many others exist, unlike the time-based versions.
The two formatting options exist for the databases and APIs that will not accept the canonical dashes: hyphens can be removed to leave a bare thirty-two character string, and the result can be upper-cased. Either way the value is the same identifier, so choose whichever form the receiving system validates against. Randomness comes from the platform cryptographic generator, not from a predictable pseudo-random sequence, which is what makes these safe to use as unguessable tokens as well as identifiers.
How to use UUID Generator
- 1 Set how many identifiers you need, up to a hundred.
- 2 Choose whether the hyphens should be kept and whether the output should be upper case.
- 3 Copy the list and generate a fresh one for each record rather than reusing a value.
Frequently asked questions
Can two generated identifiers ever be the same?
The chance is negligible. With 122 bits of randomness the number of possible values is astronomically larger than any realistic number of records, and collision is a theoretical concern rather than a practical one. The identifiers are not, however, sequential, so do not rely on them for ordering.
Why does the version number appear in the middle?
The specification reserves those bits to declare the version and the variant, so a compliant version 4 identifier always carries them in fixed positions. That is how a receiving system can tell which kind of identifier it has been given without any external metadata.
Should I use these as primary keys in a database?
They work, but consider the cost. They are larger than an integer and, being random, they scatter inserts across the index rather than appending them, which slows writes at scale. A time-ordered identifier is usually the better choice when the key will be the clustering key.
Is it safe to generate identifiers in the browser?
That is the design: the values come from the platform cryptographic random source, so nothing predictable is involved and no round trip to a server is needed. The generation happens locally, which also means it works on a page with no network access.
Free, online, and private
Free to use
UUID Generator is completely free. There is no account to create, no login, and no hidden charge or usage limit.
Runs online in your browser
It is a free online tool that runs entirely in your browser. Nothing to download or install — open the page and start using it right away.
Your data stays private
All processing happens locally on your device. Your input is never uploaded, stored, or tracked, so it never leaves your browser.
How UUID Generator behaves in detail
These are the specifics of this implementation — the exact ranges, defaults and fixed settings you are working with.
| Parameter | Value |
|---|---|
| Version | UUID v4 (random) |
| Batch size | 1 – 100 per click (default 1) |
| Randomness source | crypto.randomUUID where available |
| Formatting options | uppercase, and hyphens removed |
| Output shape | 8-4-4-4-12 hex digits, 36 characters with hyphens |
Compiled from the implementation of this tool and checked against it by itoolnet.
What UUID Generator does not do
Knowing the edges of a tool saves more time than another list of its features. These are the cases where it will not do what you might expect.
- Only version 4 (random) UUIDs are produced. Time-based v1 and name-based v3/v5 are different algorithms with different ordering guarantees, and neither is available here.
- Hyphens can be removed but no other separator is offered — no braced form, no URN prefix (urn:uuid:), and no way to insert a custom delimiter.
Tested and documented by itoolnet, the team that builds and maintains this site.