Every UUID version, and which to use.
Make UUIDs of every version in RFC 9562 by the thousand, and read any UUID back to its version and, for versions 1, 6 and 7, the time it was made.
By Suraj KumarUpdated 4 min read
A UUID is 128 bits written as 32 hex digits. RFC 9562 (2024) defines eight versions, and they differ in what those bits hold: nothing but chance, the time, or a name.
Make one, or 100,000.
Open the UUID generator, choose the version and how many, and they are made at once on your device with your browser's own cryptographic randomness. Copy them or download them as lines, a JSON array, CSV or SQL rows, in lower or upper case, with or without hyphens.
Which version.
Version 4 is 122 random bits and says nothing about where or when it was made: the safe choice for most IDs. Version 7 starts with the time in milliseconds, so new UUIDs sort after old ones, which keeps a database index compact; IDs made in the same millisecond still sort, by a counter. Versions 1 and 6 hold a finer time and a node, here a random one, never your network card.
Versions 3, 5 and 8 make the same UUID from the same namespace and name every time, with MD5, SHA-1 or SHA-256, which suits IDs for things that already have a name, such as a URL. The nil and max UUIDs are all zeros and all ones.
Read a UUID.
Paste any UUID, in braces, as a URN or without hyphens, and see its version and variant; for versions 1, 6 and 7, the moment it was made, in UTC and your own time.
Nothing leaves your browser.
Everything is worked out on your device: what you paste or open is never sent anywhere, and nothing is kept when you leave. A share link carries what you typed after the #, which browsers never send to a server.
Further reading
Topics: uuid generator · uuid v4 · uuid v7 · uuid v7 generator · uuid v4 vs v7 · guid generator · uuid version · uuid decoder · rfc 9562
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