- Press a button to mint a UUID. Click any value to copy it.
Why this exists
Most UUID pages stop at a random v4 and call it done. The interesting work is the other direction: a v1, v6, or v7 UUID carries the moment it was minted in fixed bit positions, so a value you already have in a log or a database row will tell you when it was created. Paste one above and the decoder pulls the version, the variant, and the embedded timestamp straight out of the bytes. Nothing leaves your browser.
Frequently asked questions
- What is the difference between v4 and v7?
- A v4 UUID is 122 random bits, so two made a millisecond apart sort nowhere near each other. A v7 UUID puts a 48-bit Unix millisecond timestamp in the front, so they sort by creation time. v7 is the better default for database keys because time-ordered inserts keep a B-tree index from fragmenting.
- Can you really read the time out of a UUID?
- Out of some of them. v1, v6, and v7 all store a timestamp in fixed bit positions, so paste one here and the decoder shows the exact moment it was minted. v4 is pure randomness with no embedded time, and v3 and v5 are hashes, so those tell you nothing about when they were made.
- Is the timestamp accurate?
- For v7 it is the generator's wall clock to the millisecond. For v1 and v6 it is 100-nanosecond intervals counted from 15 October 1582, which the decoder converts to a normal date. The clock is only as trustworthy as the machine that minted the UUID, so a wrong system clock makes a wrong embedded time.
- Is this random enough to use?
- Yes. Generation uses the browser's crypto.getRandomValues, the same cryptographically secure source the platform exposes to everything else. Nothing is generated on a server; it all happens in your browser.
- What is the variant field?
- Two or three bits that say which UUID layout standard a value follows. Almost everything you will see is the RFC 9562 variant (the bits 10xx). The decoder also flags the older NCS, the Microsoft GUID, and the reserved variants when it sees them.
- Does it track me or use cookies?
- No. No ads, no analytics, no third-party scripts. Everything runs in your browser and nothing is sent anywhere.