How the UUID Generator works
A UUID is a 128-bit value written as 32 hexadecimal digits in five groups (8-4-4-4-12). Four bits hold the
version and two bits hold the variant, as defined in RFC 9562. The generator fills the remaining bits in your
browser with crypto.getRandomValues, the operating system's cryptographically secure random
number generator.
Version 4 UUIDs use 122 random bits, so they reveal nothing about when or where they were made. Version 7 UUIDs start with a 48-bit Unix timestamp in milliseconds, followed by a 12-bit counter and 62 random bits. Because the timestamp comes first, v7 values sort in creation order, which keeps database indexes compact. When several UUIDs are created in the same millisecond the counter is incremented, so every list the tool produces is in strictly increasing order.
How to use the UUID Generator
- Choose Version 4 for fully random UUIDs or Version 7 for UUIDs that sort by creation time.
- Enter how many UUIDs you need, from 1 to 10,000.
- Tick Uppercase, untick Hyphens or tick Wrap in braces to change the format. Ten UUIDs are generated when the page opens, and changing an option generates a new list.
- Select Generate UUIDs, or press Ctrl + Enter (Cmd + Enter on a Mac), to create a fresh list.
- Copy the list or download it as a .txt file.
Example
Generating 3 version 7 UUIDs gives values like these (yours will differ):
01920c7e-9a41-713c-8f0e-5b2d61c4e7a9
01920c7e-9a41-713d-b41c-09e37f5a2d18
01920c7e-9a41-713e-9d77-c2a8e0b6f351
All three share the timestamp prefix 01920c7e-9a41. The 7 at the start of the third group
is the version, and the counter after it (13c, 13d, 13e) keeps them in order.
With Uppercase on, Hyphens off and braces on, a version 4 UUID looks like
{3F2504E04F8941D39A0C0305E82C3301}.
Common use cases
- Creating primary keys for test rows or seed data before inserting them into a database.
- Generating time-ordered v7 IDs to check how they behave in an index compared with random v4 IDs.
- Getting correlation or request IDs to paste into API calls, log searches or configuration files.
- Producing a large batch of unique identifiers for a spreadsheet or import file.
Frequently asked questions
What is the difference between UUID v4 and v7?
A version 4 UUID is 122 random bits. A version 7 UUID starts with a 48-bit Unix timestamp in milliseconds followed by random bits, so v7 values sort in the order they were created. That makes v7 a better choice for database primary keys, while v4 reveals nothing about when it was made.
Are the UUIDs really random and unique?
The random bits come from crypto.getRandomValues, the browser's cryptographically secure random number generator. With 122 random bits, the chance of two v4 UUIDs ever colliding is negligible for any realistic number of IDs.
Are v7 UUIDs in order if many are created in the same millisecond?
Yes. The 12 bits after the version hold a counter that increases for each UUID created within the same millisecond, as described in RFC 9562. If the counter runs out, the next millisecond is used, so every list the tool generates is in strictly increasing order.
Which version and variant bits are set?
The 13th hexadecimal digit is the version (4 or 7) and the 17th digit is 8, 9, a or b, which marks the RFC 9562 variant. Hyphens, uppercase letters and braces only change how the value is written, not its bits.
Are generated UUIDs sent to your server?
No. They are generated by JavaScript in your browser and are not uploaded or stored.