UUID generator
Create universally unique identifiers in your browser. Version 4 is fully random; version 7 starts with the current time so new ids sort after older ones. Generate up to 100 at a time.
Runs in your browser: nothing you enter is sent anywhere.
How to use it
- Choose version 4 or 7.
- Set how many you need.
- Choose uppercase or remove the hyphens if your system wants that format.
- Copy the list, or press Generate again for new ones.
How it works
A UUID is 128 bits, written as 32 hex digits in groups of 8-4-4-4-12. The 13th digit shows the version (4 or 7) and the first digit of the fourth group is 8, 9, a or b, which marks the RFC variant.
For v7, the first 48 bits are the current time in milliseconds, so for example the timestamp 1645557742000 starts a UUID with 017f22e2-79b0-7…. The remaining bits are random.
Tips
- Use v7 for database primary keys; random v4 values spread inserts across an index.
- Ids with no hyphens are 32 characters and some APIs require exactly that.
- Ids made in the same millisecond share a prefix in v7 but differ in their random part; they are not guaranteed to be in creation order within that millisecond.
Frequently asked questions
What is the difference between UUID v4 and v7?
Version 4 has 122 random bits and no order. Version 7 (RFC 9562) begins with a 48-bit Unix timestamp in milliseconds followed by random bits, so ids created later sort later, which keeps database indexes tidy.
Can two UUIDs be the same?
In practice no. A v4 UUID has 122 random bits, so the chance of a repeat among billions of ids is negligible, as long as the random source is good. This tool uses crypto.getRandomValues.
Is a UUID a secret?
Not necessarily. v7 reveals when it was created, and an id is not an access token. Do not rely on a UUID alone to protect private data.
Is a GUID the same thing?
Yes. GUID is Microsoft's name for the same 128-bit identifier, usually written in uppercase, which you can get with the Uppercase option.
Are the ids stored anywhere?
No. They are created in your browser and exist only on this page.