About the UUID Generator
A UUID (Universally Unique Identifier) is a 128-bit ID written as 32 hex digits in 8-4-4-4-12 groups, like 550e8400-e29b-41d4-a716-446655440000. Because they can be created anywhere without a central server and practically never collide, UUIDs are used for database keys, file names, request and trace IDs. Microsoft calls the same thing a GUID.
This generator uses your browser’s cryptographically secure random numbers (Web Crypto API), and v7 follows the current standard, RFC 9562.
How to use
- Pick v4 or v7 and enter how many you need (1–100).
- Optionally turn on uppercase, no hyphens, braces, or quotes & commas (for code arrays). Only the formatting of the current values changes.
- Click Copy all or Copy on a single line, or Save .txt to download them as a file.
- Paste any UUID into the UUID validator to see whether it is valid, which version it is and, for v1, v6 and v7, when it was created.
UUID versions compared
| Version | Built from | Notes |
|---|---|---|
| v1 | Timestamp + MAC address | Can leak device information |
| v3 / v5 | MD5 / SHA-1 hash of a name | Same input, same UUID |
| v4 | 122 random bits | Most common, no ordering |
| v7 | Unix time in ms + random bits | Time-sortable, index-friendly |
The 13th hex digit (first character of the third group) is the version number: xxxxxxxx-xxxx-7xxx-… is a v7 UUID.
Why v7 is better for database primary keys
v4 values are completely random, so inserting them into a B-tree index (MySQL InnoDB, PostgreSQL) scatters writes across the index, causing page splits and cache misses. v7 starts with a 48-bit timestamp, so new IDs are always appended at the end of the index – almost as fast as an auto-increment key, yet still generated on any server without coordination. The creation time is visible in the ID, though, so use v4 where that must not be exposed.
FAQ
Can two UUIDs ever collide?
A v4 UUID has 2^122 (about 5.3×10^36) possible values. You would have to generate a billion per second for about 85 years to reach a 50% chance of a single duplicate, so in practice they are unique.
What is the difference between a GUID and a UUID?
None – both are the same 128-bit identifier. In the Microsoft world it is called GUID and usually written in uppercase with braces {…}. Turn on Uppercase and Braces to get that format.
Are the generated UUIDs sent or logged anywhere?
No. UUIDs are created in your browser and never leave your device. Only your format options and count are remembered on this device.
Are v7 UUIDs created in the same millisecond still in order?
Yes. Within one millisecond the generator uses the counter method from RFC 9562, so each new value is always larger. A batch of 100 sorts exactly in creation order.