UUID Generator

Generate cryptographically random UUID v4 identifiers, one at a time or in bulk.

About UUIDs

A UUID (Universally Unique Identifier) is a 128-bit identifier formatted as 32 hexadecimal characters in five hyphen-separated groups: xxxxxxxx-xxxx-Mxxx-Nxxx-xxxxxxxxxxxx. The M position encodes the UUID version; the N position encodes the variant.

What is version 4?

UUID v4 is the random variant: 122 of the 128 bits are filled with cryptographically random data, and the remaining six are reserved for the version and variant markers. With 2122 possible values, the practical probability of a collision is negligible for almost every application.

How this tool generates UUIDs

Modern browsers expose crypto.randomUUID(), which is what this tool uses when available. Where it is not, the tool falls back to crypto.getRandomValues() with the same bit layout, so the output remains a valid v4 UUID.

Privacy

All randomness is generated locally by your browser. No network request is made, so the UUIDs you generate are unique to your session.

Frequently asked questions

Are these UUIDs safe to use as database keys?
Yes. UUID v4 has 122 bits of randomness, which is more than enough entropy for primary keys in most databases. If insertion locality matters for indexing, consider UUID v7 or ULIDs instead.
Why are there other UUID versions?
Versions 1 and 6 mix in a MAC address and timestamp. Version 5 derives the UUID from a name in a namespace using SHA-1. Version 7 puts a millisecond timestamp at the front so the UUIDs sort by creation time. v4 is the simplest and most common.
Can I generate UUIDs without hyphens or in uppercase?
Yes. Use the formatting toggles above to switch between lowercase / uppercase and to remove hyphens. The underlying value is identical, just rendered differently.
Is the randomness truly secure?
It uses the operating system's cryptographically secure random number generator via the Web Crypto API, the same source used for generating cryptographic keys in the browser.