UUID Generator
Version 4 UUIDs built from your browser's cryptographic random number generator — the same source used for key material, not Math.random.
How to use the UUID Generator
- Set how many UUIDs you need, up to 500 in one batch.
- Pick a format — standard, uppercase, braces, no hyphens or URN.
- Press Generate, then copy the list or download it as a text file.
What version 4 means
A UUID is 128 bits written as 32 hexadecimal digits. Version 4 fills those bits with random data, apart from six that identify the version and variant — which is why the third group always begins with 4 and the fourth begins with 8, 9, a or b. That leaves 122 random bits.
Other versions exist and solve different problems: v1 embeds a timestamp and MAC address, v5 hashes a name into a namespace deterministically, and v7 (newer) is time-ordered for better database index locality. Version 4 is the right default when you simply need an identifier that nobody else will generate.
Are collisions realistic?
No, at any scale you are likely to reach. With 122 random bits you would need to generate roughly 2.7 × 10¹⁸ UUIDs before the chance of a single collision reaches 50%. Generating a billion per second, that is about 85 years.
The practical risk is never the maths — it is a weak random source. This tool uses crypto.getRandomValues, which draws from the operating system's cryptographic generator. Implementations built on Math.random are genuinely collision-prone and should not be used for identifiers that matter.
A note on databases
Random UUIDs make poor clustered primary keys. Because each new value lands at an unpredictable point in the index, inserts scatter across pages and fragment the B-tree. If you are choosing a key for a large table, consider UUID v7 or a sortable ID scheme instead, or keep an auto-increment key internally and expose the UUID publicly.
Frequently asked questions
Are these safe to use as security tokens?
They are generated from a cryptographic source, so they are unguessable. But a UUID has no expiry, no signature and no scope. For session tokens, prefer a purpose-built token format with an expiry.
What is the difference between UUID and GUID?
None technically. GUID is Microsoft's name for the same 128-bit standard. Microsoft tooling often wraps them in braces, which is why that format is offered here.
Do the same UUIDs appear for other visitors?
No. Generation happens in your browser with your own random source. Nothing is sent to or stored on a server, so no two visitors share a sequence.
Can I generate a v1 or v5 UUID here?
Not currently — this tool produces version 4 only. Version 1 would leak your machine's identity, and version 5 needs a namespace and name that only make sense in your application.
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