UUID generator
Generate version 4 (random) or version 7 (time-ordered) UUIDs, and check any UUID you already have.
Runs entirely in your browser
Check a UUID
- Version
- -
- Variant
- -
- Timestamp (UTC)
- -
1 to 1,000 UUIDs at a time.
How to generate UUIDs
- Choose version 4 for fully random identifiers, or version 7 for identifiers that sort by creation time.
- Set how many you need and any format options: uppercase, no hyphens, or braces.
- Copy the list or download it as a text file. Paste a UUID into the checker to read its version.
What a UUID is, and v4 against v7
A UUID is a 128-bit identifier written as 32 hex digits in five groups. Because the space is so large, systems can create IDs independently, with no central counter, and still expect them to be unique.
In a version 4 UUID, 122 of the 128 bits are random; the rest hold the version (4) and the variant. A version 7 UUID starts with the creation time in Unix milliseconds, followed by a counter and random bits. Because the time comes first, newer IDs sort after older ones, which is friendlier to database indexes than fully random keys. The cost is that the creation time can be read from the ID.
This tool uses the browser's secure random generator. Within one millisecond, version 7 values increase through a 12-bit counter, so a batch is strictly ordered.
Tips
- Need a password rather than an ID? Use the password generator.
- Turn an ID into a scannable code with the QR code generator.
Questions
Which version should I use?
Version 4 is 122 random bits and is the usual default. Version 7 puts a millisecond Unix timestamp first, so values sort in creation order, which keeps database indexes tidy. Use v7 when ordering matters and you are happy for the creation time to be readable from the ID.
Are the UUIDs sent anywhere?
No. They are generated in your browser from its secure random number generator and are not sent or stored.
Can two UUIDs collide?
For version 4 the chance is negligible: you would need to generate billions per second for years to see a realistic risk. Version 7 values created in the same millisecond are kept distinct and increasing by a counter in the random bits.
Is a GUID the same as a UUID?
GUID is Microsoft's name for the same 128-bit format. Some tools write GUIDs in uppercase or inside braces, which the options here can do.
What does the checker read?
It accepts a UUID with or without hyphens, braces or a urn:uuid: prefix, and reports the version, the variant and, for version 7, the timestamp stored in the first 48 bits. It cannot tell whether an ID was actually issued by anything.
Is the version 7 layout standard?
Yes. It follows RFC 9562: 48 bits of Unix milliseconds, the version, a 12-bit counter, the variant and 62 random bits.