UUID Generator
Set a quantity and generate — every UUID is created fresh in your browser using a cryptographically secure random source, nothing is uploaded.
A native browser API, nothing hand-rolled
This generator calls crypto.randomUUID() directly —
a built-in browser method that returns a spec-compliant version 4
UUID in one call, backed by the same cryptographically secure
random number generator used for keys and tokens. There's no
library to load and no manual bit-twiddling: it's supported
natively across all current versions of every major browser this
site targets. Your uppercase choice is applied to the result
afterward as a simple text transform — it doesn't change how the
UUID was generated.
Worked example
Generating one UUID might produce 502fb771-2b2b-4f9f-bb91-ffc7ee8269f2. Look at the 4 at the start of the third group — that's the fixed
version digit marking this as v4 — and the b at the
start of the fourth group, which is always one of 8, 9, a, b, the fixed RFC 4122 variant bits.
Everything else in those 32 hex digits is random. Ticking
"Uppercase" turns it into 502FB771-2B2B-4F9F-BB91-FFC7EE8269F2 — same UUID,
same value, just a different text case.
Frequently asked questions
How random is a v4 UUID, really?
Version 4 UUIDs are generated purely from randomness — this tool uses crypto.randomUUID(), the browser's built-in cryptographically secure random number generator (not Math.random(), which isn't safe for this). Out of the 128 total bits, 122 are random; the remaining 6 are fixed to mark the UUID as version 4 (the 4 at the start of the third group) and set the RFC 4122 variant (the first character of the fourth group is always 8, 9, a, or b). That's different from version 1 UUIDs, which encode the current timestamp and a node identifier — v1 IDs reveal roughly when they were created, v4 IDs reveal nothing but themselves.
What are the odds two generated UUIDs collide?
Astronomically low. With 122 random bits, the space of possible v4 UUIDs is 2^122 — roughly 5.3 undecillion values. Even generating a billion UUIDs per second, it would take about 85 years before the probability of a single collision anywhere reached 50%. In practice, treat v4 UUIDs as unique for any real-world workload; the risk of a bug elsewhere in your system is vastly higher than the risk of a random collision.
Why is a UUID 36 characters long?
A UUID is 128 bits, written as 32 hexadecimal digits grouped 8-4-4-4-12 and joined with four hyphens: 32 digits + 4 hyphens = 36 characters. The grouping is purely a legibility convention from the original spec — the hyphens carry no information — which is why some systems strip them for a compact 32-character form.
Should UUIDs be uppercase or lowercase?
RFC 4122 specifies lowercase hex digits as the canonical form, and that's what this tool produces by default. Uppercase UUIDs are functionally identical — some codebases and legacy systems (notably certain Microsoft GUID conventions) prefer uppercase by convention — which is why an uppercase toggle is offered here, but lowercase is the safer default if you have no specific reason to change it.