UUID Generator
Random version-4 UUIDs, one or ten thousand, from your browser's cryptographic random source.
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Click New for another. Nothing is stored, and nothing is sent anywhere.
What the 36 characters are
A UUID is 128 bits written as 32 hex digits in five hyphen-separated groups: xxxxxxxx-xxxx-Mxxx-Nxxx-xxxxxxxxxxxx.
- M — the version nibble. A
4here means "generated from random data". - N — the variant. For RFC 4122 UUIDs it is always
8,9,aorb. - The remaining 122 bits are random, and on this page they come from
crypto.getRandomValues()— the operating system's cryptographic random source, notMath.random().
The hyphens carry no information. Strip them if your database stores a CHAR(32); a UUID is the same value either way, and so is uppercase versus lowercase.
About this tool
UUIDs exist so two machines that have never spoken to each other can each invent an identifier and be confident the two will not clash. That is why they turn up as database keys, request ids, S3 object names, device ids and file names.
Version 4 is the one people almost always mean. It is pure randomness, which is its strength — no coordination, no central counter — and also its one weakness: because consecutive values are unordered, they land all over a database index instead of at the end of it. If you are generating millions of rows, store them as 16 raw bytes, or reach for a time-ordered id like UUIDv7 or ULID.
Every value on this page is generated in your browser. This site never sees the UUIDs you copy, which is not true of generators that call an API to produce them.
FAQ
Which UUID version does this generate?
Version 4 — the fully random one. 122 of its 128 bits come from your browser's cryptographic random source; the other 6 are fixed by RFC 4122 to record the version and variant. The inspector above reads any version, but the generator only produces v4.
Are these UUIDs really unique?
For practical purposes, yes. With 122 random bits you'd need to generate roughly 2.7 quintillion UUIDs before there's even a one-in-a-billion chance of a single collision. They aren't guaranteed unique — they're unique the way winning the lottery ten times running is impossible.
Are they generated on a server?
No, and that matters. Every UUID is generated in your browser and never leaves this page, so nobody — including this site — has seen the values you copy.
Should I use a UUID as a database primary key?
You can, but v4 UUIDs are random, so they scatter inserts across a B-tree index and fragment it. Store them as 16 raw bytes rather than a 36-character string, or use a time-ordered id such as UUIDv7 or ULID when insert performance matters.
Is a UUID a secret?
A v4 UUID is unguessable, so it's fine as an unlisted link or an object name. It is not an authentication token: it never expires, it can't be revoked, and it ends up in logs, referrers and browser history.