UUID Generator

What a UUID is

A UUID (Universally Unique Identifier) is a 128-bit value written as 32 hexadecimal digits in five groups, for example 123e4567-e89b-42d3-a456-426614174000. Developers use them as IDs for database records, files and sessions when they need a value that will not clash with others, even when created on different machines without coordination.

Version 4 and how unique it is

This tool creates version 4 UUIDs, which are random apart from a few fixed bits that mark the version. That leaves 122 random bits, so the chance of a duplicate is negligible: you would need to generate billions of IDs per second for decades before a clash became likely.

When to use them

• Public identifiers that should not be guessable or countable, unlike sequential numbers.
• Merging data from several systems.
• Test data and temporary file names.

Frequently asked questions

Are UUIDs secure tokens?

They are hard to guess, but they are not designed as secrets. For login or reset tokens, use a cryptographically secure token generator and expiry rules.