UUID Generator
Generate RFC 4122 compliant UUID v4 identifiers. Generate 1–10 UUIDs at once.
What a UUID is and what this tool makes
A UUID (Universally Unique Identifier) is a 128-bit number written as 32 hexadecimal digits in five groups separated by hyphens. An example in the right format is b7e2c1a4-58d3-4f0e-9c6b-2a1d7e90f4b8. This generator produces version 4 UUIDs, which are made from random bits. In a version 4 value the third group always begins with 4, and the fourth group begins with 8, 9, a or b.
How to generate UUIDs
- Open the How many? list and choose a number from 1 to 10. It starts at 5.
- Click Generate. The list is replaced with new values, and the previous ones are discarded.
- Click the copy icon beside a single UUID to copy only that value.
- Click Copy All to copy every value on the list, one per line.
The count list has no effect until you click Generate, because the current list is only rebuilt at that point.
Worked example
Suppose you are writing a seed file with three test records. Set How many? to 3, click Generate, then click Copy All. Paste the three lines into the file. Each line is an independent identifier, so you can use them as primary keys without checking them against each other. The chance of two random version 4 values colliding is negligible for ordinary projects.
How the values are created
Each UUID is produced in your browser with crypto.getRandomValues, the Web Crypto source of random bytes. The code then sets the version and variant bits that RFC 4122 requires. Nothing is sent to a server, and the page does not keep a history of what you generated.
Tips and limits
- Use a UUID as an identifier, not a secret. Session tokens and passwords need their own generator with a defined length and a clear security design.
- Random values are not time-ordered. Random version 4 UUIDs can spread out database index writes. If you need time-ordered identifiers, look for UUID version 7, which this tool does not generate.
- GUID is the same format. Microsoft uses the name GUID for these 128-bit values, so the output works wherever a GUID is expected.
- Copy values right away. Clicking Generate again replaces the list.
UUID Generator – Frequently Asked Questions
What is a UUID?
A UUID (Universally Unique Identifier) is a 128-bit identifier written as 32 hexadecimal digits in five hyphen-separated groups. Software uses UUIDs to identify records and objects without a central authority issuing numbers.
What version of UUID does this generate?
This tool generates UUID version 4, which is built from random bits and follows RFC 4122. The values are created in your browser with the Web Crypto random number generator, not with Math.random.
Are these UUIDs truly unique?
A version 4 UUID has 122 random bits, so the chance that two random values match is extremely small. In practice they are treated as unique, but the tool does not check them against a database.
What is the difference between a UUID and a GUID?
GUID (Globally Unique Identifier) is Microsoft's name for the same 128-bit format defined by the UUID standard. A GUID and a UUID are written the same way and are interchangeable.
Are the generated UUIDs sent to a server?
No. They are created and displayed in your browser. The page does not send or store them.