UUID Generator

Generate random version 4 UUIDs (GUIDs), one at a time or up to a hundred at once. Each one comes from your browser's cryptographic random number generator and never leaves this page.

Options

Between 1 and 100. The list regenerates as you type.
All four describe the same UUID; pick the shape your system expects.
Your format choice is remembered in this browser. The UUIDs themselves are never saved.

UUIDs

Generate a set to see how many were made.

Private by design. This page has no backend. UUIDs are computed by JavaScript on your own device and are never transmitted or stored.

What a UUID is

A UUID (universally unique identifier, also called a GUID) is a 128-bit value written as 32 hexadecimal digits in five groups. The point is that you can make one up on any machine, at any time, without asking a central server first — the number of possible values is so large that accidental collisions are vanishingly rare.

Why version 4

Version 4 fills 122 of those 128 bits with random data; the remaining 6 record the version and variant, which is how software recognises it. The odds of two v4 UUIDs colliding are below one in a hundred billion even after generating a billion of them, which is why databases, distributed systems and API responses rely on them.

How these are made

With crypto.getRandomValues, the browser's cryptographic generator, filling 16 bytes. The version and variant bits are stamped in exactly as RFC 4122 requires, and the result is formatted to your chosen style. If that API is unavailable the page warns you above, rather than quietly producing weaker identifiers.

Choosing a format

Plain lowercase is what most databases and APIs expect. Uppercase is equally valid — hex digits are case-insensitive — and some Windows tooling displays it that way. Braces ({…}) are the Microsoft style seen in the registry and .NET. The urn:uuid: prefix appears in XML documents and some standards-track file formats.

Common uses

Primary keys for database rows that are created offline, correlation IDs in log lines, test fixtures, idempotency keys for API requests, and unique file or resource names.

How to use the UUID Generator

  1. Choose how many UUIDs you need.
  2. Pick any formatting options — uppercase, braces or the urn:uuid prefix.
  3. Generate and copy one, or copy all of them at once.

Frequently asked questions

Which UUID version is generated?

Random version 4 UUIDs, produced with your browser's cryptographic random generator.

Can I make more than one at a time?

Yes. Set the count to generate a batch, then copy them all in one go.

Are the UUIDs guaranteed unique?

Version 4 UUIDs have 122 random bits, so a collision is practically impossible.