UUID v4 Generator

What does this tool do?

A UUID v4 is a 128-bit identifier based on randomness. Use it to identify records, requests and test data without a central counter. This tool uses the browser crypto.randomUUID API and generates between 1 and 100 UUIDs per run. Collisions are very unlikely with a good generator, but uniqueness is probabilistic rather than guaranteed.

How to use it

1. Enter an integer quantity from 1 to 100. For the example, use 1.
2. Select Generate UUID. Each identifier appears on a separate line and changes on every run.
3. Check the hyphen-separated hexadecimal 8-4-4-4-12 structure. The third group starts with 4; the fourth starts with 8, 9, a or b.
4. Select Copy result to copy all lines. If your system requires uniqueness, also enforce a constraint and handle collisions at the destination.

Input and output examples

1

fa4ad55f-6d46-4df2-9db2-fb57b3893687

Important limitations

• Generates only UUID v4. Other versions, custom values, chronological ordering and deterministic generation from a seed are not supported.
• Requires browser support for crypto.randomUUID, a secure-context API. If unavailable or failing, it displays an error without using a fallback generator.
• Does not record generated values or check duplicates within the list or against other systems. Global uniqueness is not guaranteed.
• The limit is 100 per run. A UUID does not replace authentication, authorization or an access secret.

Common mistakes

• Entering an empty, fractional, below-1 or above-100 quantity.
• Expecting the same output when repeating a quantity or using the example as a fixed production value.
• Using UUID v4 to sort records by time: it does not encode chronological order.
• Treating a hard-to-guess identifier as access permission or assuming it can never repeat.

Frequently asked questions