UUID generator
Runs in your browser; nothing is uploaded
Generate version 4 or version 7 UUIDs, one or a thousand at a time, and inspect any UUID's version, variant and timestamp.
Generated
Generating…
Inspect
Shows the version, the variant and, for time-based UUIDs (versions 1, 6 and 7), when it was made. Choose Inspect on a generated value to try it.
What is a UUID?
A UUID (universally unique identifier), also called a GUID, is a 128-bit value written as 32 hex digits in five groups, like 3f2b8c1e-9a4d-4e7b-b5c2-6d1f0a8e9c47. Anyone can create one without asking a central server and still be practically certain no one else will create the same value. RFC 9562 defines the formats.
Version 4 is random: 122 of its 128 bits come from a secure random generator. Version 7 starts with the Unix time in milliseconds followed by random bits, so values sort by creation time. That makes v7 a better database key, because new rows go to the end of an index instead of random places. You can tell the version from the first digit of the third group: 4 or 7.
APIs use UUIDs as resource IDs, idempotency keys and request IDs. In tests they give each run unique names and keys, and a well-formed UUID that doesn't exist is a good way to check that an API answers 404 rather than 500.
How to use this tool
- 1Choose v4 random or v7 time-ordered, how many you want (up to 1,000), and press Generate or Ctrl+Enter.
- 2Pick the written form: uppercase, with or without dashes, in braces as GUIDs often are, or with the
urn:uuid:prefix. The list updates without generating new values. - 3Copy one value with the button on its row, or the whole list with Copy all. Download (Ctrl+S) saves the list as a text file, one per line.
- 4Paste any UUID into Inspect, or choose Inspect on a generated row, to see its version, its variant and, for versions 1, 6 and 7, when it was made.
Troubleshooting
- Inspect says the value has the wrong number of digits
- A UUID has exactly 32 hex digits. Values copied from logs are sometimes cut off or have extra characters attached; braces, dashes and a
urn:uuid:prefix are accepted. - The variant is not RFC 9562
- Older Microsoft and NCS formats use other variant bits. For those values the version digit doesn't mean what RFC 9562 says, so the tool reports the variant and leaves the rest alone.
- v7 values from two browser tabs don't sort perfectly
- Within one batch the tool keeps v7 values strictly increasing, even inside the same millisecond. Values from separate tabs or machines made in the same millisecond can interleave, as the RFC allows.
Frequently asked questions
Can two UUIDs ever be the same?
In practice, no. With 122 random bits (or 74 per millisecond for v7) you would have to generate billions per second for many years before a duplicate became likely.
Are these UUIDs safe to use as secrets?
They come from your browser's secure random generator, but a UUID is an identifier, not a secret, and v7 reveals when it was made. Use the password generator for tokens and keys.
Are the UUIDs generated on a server?
No. They are generated in your browser after the page loads, and they aren't stored or sent anywhere.