Generate random UUIDv4 and GUID identifiers in single or batch modes.
A UUID (universally unique identifier, called a GUID in the Microsoft world) is a 128-bit number written as 32 hex digits in five groups, like 3f2b8c1e-7d4a-4f6b-9c2e-5a1d8e7f0b3c. A version 4 UUID is almost entirely random: 122 of the 128 bits are random, and the other 6 only mark the version and variant. You can recognise a v4 by the 4 at the start of the third group.
Because there's no central registry, anyone can create one at any time and still be confident it's unique. That's the point: a database, a phone app and a server can each create IDs without checking with each other.
In theory yes, in practice no. With 2^122 possible values, you'd need to generate about 2.7 quintillion (2.7 × 10^18) UUIDs before there's even a 50% chance of a single duplicate. At a billion per second, that takes around 85 years.
That only holds if the random numbers are good. This tool uses the browser's crypto.randomUUID(), which draws on the operating system's cryptographic random source, not Math.random().
Random v4 UUIDs work well for IDs that show up in URLs or APIs, since nobody can guess the next one or tell how many records you have. The trade-off is that they arrive in random order, which can slow down very large indexes in databases like MySQL or SQL Server. If that worries you, look at UUID version 7, which begins with a timestamp so new IDs sort in order. For most apps, v4 is perfectly fine.
Yes. GUID is Microsoft's name for the same 128-bit format. Some Microsoft tools show them in uppercase with braces, which you can switch on here.
They come from a cryptographic random source, so they're unpredictable. Still, for passwords, API keys or password-reset links, a purpose-built random token is the better habit. A UUID is meant to be an identifier, not a secret.
No. Hyphens are only formatting; the 32 hex digits without them are the same value, and most systems accept either form.
No. They're created in your browser and disappear when you leave the page, unless you copy or download them.
OneClickly is a set of 119 free tools for PDFs, images, text, everyday math and code. They run in your browser, so the files and text you work with stay on your device.