UUID Generator

Frequently Asked Questions

Are version 4 UUIDs really unique?

They have 122 random bits, so the chance of a collision is astronomically small for any realistic number of values you will ever generate.

Is a UUID the same as a GUID?

Yes. GUID is the name Microsoft uses, but the 128-bit format and meaning are identical to a UUID.

Should UUIDs be uppercase or lowercase?

The standard form is lowercase. Many systems accept either, so match whatever your target system expects. This tool offers an uppercase toggle.

Do the UUIDs leave my browser?

No. They are generated locally with the Web Crypto API (crypto.randomUUID), so nothing is sent to a server.

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Estimates for informational purposes only.

Important Disclaimer: Estimates for informational purposes only.

This calculator provides estimates for informational purposes only. Results are based on assumptions and may not reflect actual outcomes. Consult qualified professionals in relevant fields before making important decisions based on these results.

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How This Calculator Works

A UUID (Universally Unique Identifier), also called a GUID, is a 128-bit value written as 32 hexadecimal digits in five groups separated by hyphens, such as 8-4-4-4-12. This generator creates version 4 UUIDs, which are based almost entirely on random numbers. Choose how many you need (1 to 100) and whether you want them in uppercase, then click Generate.

How It Works

Each UUID is produced in your browser using the Web Crypto API. When available, the built-in crypto.randomUUID() is used; otherwise the tool fills 16 random bytes with crypto.getRandomValues() and sets the version and variant bits by hand. Nothing is sent to a server, so the values never leave your machine.

Worked Example

Requesting 3 lowercase UUIDs might give values like 1b9d6bcd-bbfd-4b2d-9b5d-ab8dfbbd4bed, each unique. The digit in the third group is always 4 (the version), and the first digit of the fourth group is 8, 9, a, or b (the variant). Tick the uppercase box to get values like 1B9D6BCD-BBFD-4B2D-9B5D-AB8DFBBD4BED instead.

Common Mistakes

Assuming a UUID is secret or unguessable, when in fact it is only meant to be unique, not a password.

Storing UUIDs as plain text when a more compact binary column would be more efficient in a database.

Expecting version 4 UUIDs to sort in creation order; they are random, so they do not.

Pasting UUIDs with the wrong case into a system that compares them case-sensitively.

Tips & FAQ

Are these really unique? Version 4 UUIDs have 122 random bits, so the chance of a collision is astronomically small for any realistic number of values.

Is uppercase or lowercase correct? The standard form is lowercase, but many systems accept either; pick whatever your target system expects.

Is this the same as a GUID? Yes. GUID is the name Microsoft uses; the format and meaning are the same as a UUID.

Can I use these for security tokens? They are generated with a cryptographic random source, but design your security around the assumption that an identifier may be visible.

Frequently Asked Questions

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