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ToolBoxGenie

UUID Generator

Developer Tools · Added 14 July 2026

Generate version 4 UUIDs using the browser's cryptographically secure random number generator. Produce one or a thousand, switch to uppercase, strip the hyphens or wrap them in braces, then copy the lot.

Up to 1,000 at a time.

Format

How to use the uuid generator

  1. 1Set how many UUIDs you need.
  2. 2Choose your formatting: uppercase, hyphens, braces.
  3. 3Press Generate.
  4. 4Copy the whole list, or a single value with the button beside it.

Examples

Standard v4

Input
1 UUID, default format
Result
3f2a8c1e-9b4d-4f7a-a2c5-6e8d1b0f4a93

Bulk seed data

Input
500 UUIDs, uppercase, no hyphens
Result
500 32-character identifiers, one per line

About the uuid generator

Why UUIDs exist

A database auto-increment requires a single authority to hand out the next number. That works until you have several databases, or a mobile client that must create records offline, or a distributed system where round-tripping to a central sequence is too slow.

A UUID solves that by making collisions statistically impossible rather than structurally impossible. Any node can mint an identifier independently and the values will not clash.

Reading the format

The canonical form is 8-4-4-4-12 hexadecimal digits. The first digit of the third group gives the version — a 4 here means version 4 — and the first digit of the fourth group encodes the variant, which is why it is always 8, 9, a or b in the values above.

Those two fields are why a v4 UUID has 122 random bits rather than 128. It is also a quick way to identify what generated an identifier you have found in a log file.

Frequently asked questions

Are these UUIDs really unique?
A version 4 UUID has 122 random bits. Generating a billion per second for a century still leaves the chance of a single collision negligible. For practical purposes they are unique, and they are generated here with crypto.getRandomValues rather than Math.random.
What do version 1 and version 7 do differently?
Version 1 embeds a timestamp and the machine's MAC address, which leaks information and is now discouraged. Version 7 embeds a millisecond timestamp in the high bits with random low bits, so the values sort chronologically — a real advantage as a database key.
Should I use a UUID as a primary key?
It depends on the index. Random v4 values scatter across a B-tree, which fragments the index and hurts insert performance on large tables. Sequential formats such as UUIDv7 or ULID keep the locality benefits of an auto-increment while remaining globally unique.
Can I generate these offline?
Yes. Everything runs locally in your browser. No value is ever transmitted, which means a UUID generated here has genuinely only ever existed on your machine.

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