UUID Generator

How to use the UUID generator

1. Choose the UUID version: v4 for fully random identifiers or v7 for time-ordered identifiers.
2. Enter how many UUIDs you need, anywhere from 1 to 1,000.
3. Optionally enable uppercase output or remove the hyphens if the system you are feeding them into expects a compact 32-character form.
4. Generate, then copy the list to your clipboard or download it as a .txt file with one UUID per line.

What is a UUID?

A UUID (Universally Unique Identifier), also known as a GUID in the Microsoft world, is a 128-bit value used to identify something without needing a central authority to hand out numbers. It is usually written as 32 hexadecimal digits in five groups separated by hyphens, in the pattern 8-4-4-4-12, for example f47ac10b-58cc-4372-a567-0e02b2c3d479. The first digit of the third group is the version, and the first digit of the fourth group encodes the variant (8, 9, a or b for standard UUIDs).

Because any computer can create a UUID independently with a negligible chance of collision, UUIDs are widely used as database primary keys, request and correlation IDs in logs, file names for uploads, idempotency keys for APIs, and identifiers in distributed systems where several servers create records at the same time.

Version 4 vs. version 7

Both versions are defined in RFC 9562, the 2024 standard that replaced RFC 4122.

UUID v4 is almost entirely random: 122 of its 128 bits come from a random generator, and the remaining 6 bits hold the version and variant. It reveals nothing about when or where it was created. The chance of a collision is so small that you would need to generate roughly 103 trillion v4 UUIDs to reach a one-in-a-billion probability of a single duplicate. Choose v4 when you want identifiers that are opaque and carry no information.

UUID v7 starts with a 48-bit Unix timestamp in milliseconds, followed by the version, variant and 74 random bits. As a result, v7 UUIDs generated later sort after those generated earlier. This matters a lot for databases: random v4 keys are inserted at scattered positions in a B-tree index, causing page splits and poor cache locality, while v7 keys are appended near the end, much like an auto-increment integer. Choose v7 for primary keys and anything you want to sort by creation time. Keep in mind that the creation time can be read from a v7 UUID, so avoid it when that timing information is sensitive.

Randomness and security

This tool uses the browser’s cryptographically secure random number generator (the Web Crypto API), not Math.random(), which is not designed to be unpredictable. The UUIDs are generated locally on your device and are never sent to or logged by a server, so no one else ever sees the values you create.

Even so, a UUID is an identifier, not a secret. Do not rely on an unguessable UUID alone to protect a private document or a password reset link; combine it with proper authentication and expiry.

Formatting options

The canonical form is lowercase with hyphens, and RFC 9562 recommends lowercase output. Some systems, such as older Windows tools or certain databases, display GUIDs in uppercase, and some storage formats prefer the 32-character form without hyphens. Both options only change the textual representation; the underlying 128-bit value is identical, and most parsers accept all of these forms.