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UUID Generator

This UUID generator creates version 4 identifiers using the browser’s cryptographic random number generator. Values are generated locally, never stored, and can be copied as a list for tests, seed data or database keys.

Your data is processed locally in your browser and is not uploaded to our server.

How to use this tool

  1. 1 Choose how many UUIDs you need, from 1 to 100.
  2. 2 Select whether the output should be uppercase and whether hyphens should be kept.
  3. 3 Press “Generate” to create a fresh batch, or change an option to regenerate automatically.
  4. 4 Copy the list or clear the output.

Formula and calculation logic

Version 4 layout

xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx

A v4 UUID contains 122 random bits. The version nibble is fixed to 4, and the variant bits are set to 10xx, which is why the first character of the fourth group is always 8, 9, a or b.

Randomness

crypto.randomUUID() or crypto.getRandomValues()

The tool uses the browser’s cryptographic API. It does not use Math.random, so identifiers are suitable for unguessable keys, not just display values.

Worked example

A batch of five IDs

Five database keys are needed for seed data.

  1. Count: 5
  2. Lowercase with hyphens
  3. Result: five distinct v4 UUIDs

Each value is 36 characters long, including four hyphens, and the version nibble is always 4.

Compact uppercase IDs

A system stores identifiers without hyphens.

  1. Enable uppercase
  2. Disable hyphens
  3. Result: 32 uppercase hexadecimal characters per ID

The compact form carries the same 128 bits; only the presentation changes.

Edge cases and accuracy

Not a substitute for secrets

UUID v4 values are hard to guess but are not designed as passwords or API tokens. Use a dedicated secret generator for credentials.

Collisions are negligible

With 122 random bits, the chance of generating the same UUID twice is astronomically small. Duplicate protection in a database is still a good safeguard.

Maximum batch

The generator caps a batch at 100 identifiers so the page stays responsive. Generate another batch if you need more.

Frequently asked questions

What is a UUID v4? +

A 128-bit identifier with 122 random bits. Its version field is 4 and its variant bits mark it as an RFC 4122 UUID.

Are these UUIDs random enough for production? +

They are generated with the browser’s cryptographic random generator, which is appropriate for identifiers. They are not intended to replace cryptographic secrets.

Can I remove the hyphens? +

Yes. Disable “Hyphens” to get a compact 32-character hexadecimal string with the same bits.

Are the UUIDs stored anywhere? +

No. They are generated in your browser and are not sent to a server or saved.

Why does the fourth group start with 8, 9, a or b? +

Those characters encode the UUID variant bits. The fixed prefix is part of the RFC 4122 format, not a random coincidence.