UUID Generator

How It Works

A UUID (Universally Unique Identifier) is a 128-bit ID written as 32 hexadecimal digits in five groups, separated by hyphens: 8-4-4-4-12. Version 4 UUIDs are generated from random numbers, so no central registry is needed — the chance of two randomly generated UUIDs colliding is so small that, for practical purposes, every UUID is unique. That is why databases and APIs use them as primary keys and request IDs: any device can mint one without asking a server.

This generator uses your browser’s built-in cryptographic random number generator, the same source of randomness used for secure web connections, so the UUIDs are suitable for real identifiers rather than just test data. Each UUID has the version digit 4 in the third group and a variant digit of 8, 9, a or b starting the fourth group. Generation happens entirely in your browser, so your IDs are never sent anywhere.

Worked Example

A version 4 UUID looks like this: 550e8400-e29b-41d4-a716-446655440000. The third group starts with 4 (the version), and the fourth with a (the variant). Every UUID this tool generates follows the same pattern, with different random digits each time — generate a batch of 5 and you get five different IDs, one per line, ready to paste into a database, a config file or a test script.

How to Use This Tool

Choose how many UUIDs you need (from 1 to 100) and whether you want lowercase or uppercase letters, then press Generate UUIDs. The results appear one per line in the box below, with a count at the top. Press Copy All to copy the whole batch to your clipboard.

Tips and Practical Advice

• Use UUIDs when IDs must be unique across systems. Auto-incrementing numbers collide when two databases merge; UUIDs do not.
• Do not use a UUID as a password. UUIDs are identifiers, not secrets — they are designed to be unique, not to be unguessable, and a v4 UUID has only 122 bits of randomness.
• Stick to lowercase unless a system demands otherwise. Lowercase is the standard spelling, and mixing cases in the same database makes lookups and comparisons error-prone.