Toolbox

UUID Generator

Create random version 4 UUIDs in bulk — generated in your browser with the platform's secure random source.

How to generate UUIDs

  1. Choose how many identifiers you need — up to 100 in one go.
  2. Tick UPPER CASE, braces or remove the dashes if the system you are pasting into expects one of those forms.
  3. Press Generate UUIDs, then copy the list or download it as a text file.

The page generates a fresh set as soon as it loads, so there is almost always a UUID ready to copy without a click.

What a version 4 UUID actually is

A UUID — universally unique identifier — is a 128-bit value written as 32 hexadecimal digits in five groups: f47ac10b-58cc-4372-a567-0e02b2c3d479. The pattern of the groups is fixed, and two of the bits inside carry meaning. The thirteenth hexadecimal digit is the version, and for a version 4 UUID it is always a 4. The seventeenth digit is the variant, which the specification fixes to one of 8, 9, a or b. Everything else — the remaining 122 bits — is random.

Those 122 bits are the whole point. They are drawn from the browser's cryptographically secure random generator rather than a predictable sequence, so you can hand out identifiers on a server, in a mobile app and on a developer's laptop at the same time without any coordination, and still never collide. The probability is small enough that it is not worth designing around: you would have to generate trillions of UUIDs before a clash became likely.

The practical use is anywhere an identifier has to be created before it can be checked for uniqueness — a row inserted on a client, an order referenced in a URL before it reaches the database, a file name that must not be guessable. That last point matters more than people expect: a sequential identifier tells an outsider how many records you have and lets them enumerate them, while a random UUID leaks nothing and cannot be guessed.

UUID generator FAQ

Are these UUIDs really random?

Yes. The tool uses the browser's crypto.getRandomValues, the cryptographically secure random source built into the platform, and sets the version and variant bits the specification requires.

Can two UUIDs ever be the same?

A version 4 UUID holds 122 random bits, so a collision is negligible — you would need on the order of 2.7 trillion UUIDs before it became likely.

Should a UUID be a database primary key?

It works well and is a common choice, especially when records are created on different machines. The trade-off is size and index locality compared with a sequential integer, so many projects keep a numeric key internally and use the UUID as the public identifier.

What are the braces and plain options for?

Braces are the canonical form used by Microsoft tooling such as .NET Guid strings. The plain option drops the dashes, which some systems want when a UUID has to fit a fixed-width column or a file name.

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