UUID Generator
Generate version 4 UUIDs in bulk, using your browser’s cryptographic random number generator.
How to use this tool
- Fill in the options above.
- The result updates as you change the input — there is nothing to submit and nothing to wait for.
- Read the figures in the result panel.
- Use Copy or Download if you need the output elsewhere. Nothing was uploaded at any point.
These are version 4 UUIDs, meaning they are random rather than derived from a timestamp or MAC address. Randomness comes from crypto.getRandomValues, not Math.random, which matters if the identifiers will end up anywhere that collisions or guessability would be a problem.
UUID Generator — the specification
| Version | 4 (random) |
|---|---|
| Source | crypto.getRandomValues |
| Bulk | Up to 100 at a time |
| Formats | Uppercase, braces, hyphens removed |
How it works
This tool runs entirely in your browser. There is no server involved, which means nothing you type or upload is transmitted, stored, or logged — and there are no usage limits, because there is nothing for us to ration.
You can confirm it yourself: open your browser's developer tools, select the Network tab, and use the tool. No request is made.
Who needs UUID Generator
Seeding a database, generating test fixtures, or creating identifiers for records that will be merged across systems.
UUID Generator — frequently asked questions
Can two UUIDs ever collide?
In theory yes, in practice no. A version 4 UUID has 122 random bits; you would need to generate billions per second for decades before a collision became likely.
What is the difference between version 1 and version 4?
Version 1 encodes a timestamp and the machine’s MAC address, which makes it sortable but leaks information. Version 4 is pure randomness, which is why it is the usual default.
Are these safe to use as security tokens?
They are unpredictable, since they come from a cryptographic generator. But a UUID is not secret by design and often ends up in logs and URLs, so use a purpose-built token for authentication.
Does this work offline?
Yes. Once the page has loaded you can disconnect from the internet and it keeps working, because all the processing happens in your browser. That is also the simplest way to confirm nothing is being sent anywhere.
Is there a limit on how much I can paste in?
Nothing we impose. The practical limit is your device’s memory, since the work happens locally. Very large inputs get slower rather than being refused.
Can I use this on a phone?
Yes. The layout adapts to a small screen and everything works the same way.
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Background reading: Text and Developer Tools That Never Upload Your Data
Your file never leaves your device. Open your browser's Network tab while you use this page and you will see no upload — how that works.
Disclaimer. Published requirements change without notice. Confirm against the official source before you submit. Full disclaimer.