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UUID Generator: what a v4 UUID is and how to use it

A short guide to UUIDs — what version 4 is, how unique they are, where to use them, and how the generator works.

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What this tool does

The UUID Generator creates random version-4 UUIDs — one or many at a time — with optional uppercase and dash-free formatting, and one-click copy. It uses crypto.randomUUID in your browser.

What is a UUID v4?

A UUID (Universally Unique Identifier) is a 128-bit value usually written as 32 hexadecimal digits in the pattern 8-4-4-4-12, e.g. f47ac10b-58cc-4372-a567-0e02b2c3d479. Version 4 fills almost all of those bits with random data, so anyone can mint one independently and still expect it to be unique.

Are they unique?

For practical purposes, yes. A v4 UUID has 122 random bits, so the odds of two ever colliding are vanishingly small — and this tool uses a cryptographically secure random source, not Math.random.

How to use it

  1. Open the UUID Generator.
  2. Set how many you need and tick uppercase or no-dashes if you want.
  3. Press Generate, then Copy all.

Where UUIDs are used

  • Primary keys and record IDs in databases.
  • Idempotency keys and request/correlation IDs.
  • File names, test fixtures, and config identifiers.

Generated locally

Every UUID is created in your browser — none are requested from or sent to a server.

FAQ

What is a UUID v4?

A 128-bit, mostly-random identifier written as 32 hex digits in a 8-4-4-4-12 pattern.

Are these really unique?

Effectively yes — 122 random bits make collisions astronomically unlikely.

Are they generated locally?

Yes — via crypto.randomUUID in your browser.

Ready to try it? Open the UUID Generator →

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