UUID Generator

Generate UUIDs in versions 1, 3, 4, 5, 6 and 7. Choose a version, pick your options, and click Generate. All processing happens locally in your browser.

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UUID Versions Explained

VersionMethodUse Case
v1Timestamp (100-ns) + random nodeTime-ordered IDs; embeds creation time
v4Cryptographically randomGeneral-purpose unique ID - most popular
v5SHA-1 hash of namespace + nameLike v3 but uses SHA-1 (recommended over v3)
v6Reordered v1 timestampDatabase-friendly sorting of time-based IDs
v7Unix ms timestamp + randomModern time-based, monotonic, best for databases

Version 4 is the one to reach for by default: it is nothing but random bits, so it leaks nothing and collides only in theory. Version 7 is worth knowing about, because it puts the time at the front, which means a column of them sorts into the order the rows were created and a database index stays tidy instead of scattering writes. Versions 1 and 6 embed the same timestamp plus a node field; the node here is random with the multicast bit set, so it is never a real network address. Paste any UUID into the inspector and it will tell you which version it is and, where there is one, the moment it was made.

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Frequently Asked Questions

Which version should I use?
Version 4 unless you have a reason otherwise. It is random and reveals nothing. Choose version 7 when the values go into a database column that is indexed, because it sorts by creation time and keeps the index compact instead of scattering every insert.
Are these safe to use as secrets?
No. A version 4 UUID is generated from a cryptographically secure source, so it is unguessable, but it is designed to be shown, logged and passed around. Treat it as an identifier, never as a password or a session token.
Where did version 3 go?
It was removed along with MD5. Version 3 is MD5 by definition, and MD5 has practical collision attacks. Version 5 does the same job with SHA-1 and takes the same namespace and name, so switching means changing one setting.
Do two people ever generate the same UUID?
For version 4, not in practice. There are 122 random bits, which is enough that you would need to generate billions per second for a lifetime before a collision became likely. Versions 1, 6 and 7 lean on time as well, so they collide even less within one machine.
Why is the node field random?
Versions 1 and 6 originally held the machine's network address there, which leaked where a value came from. This page fills it with random bytes and sets the multicast bit, which is how the specification says to mark a node that is not a real hardware address.