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UUID Generator

Generate cryptographically random version 4 UUIDs — one, or a thousand — without touching a server.

FreeBulkCryptographic
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How it works

A compact workflow from input to download.

1

Choose how many

Generate a single UUID or a whole batch at once.

2

Generate

Each one is produced from your browser's cryptographically secure random number generator.

3

Copy them

Copy a single UUID or the whole list straight to your clipboard.

Frequently asked questions

What is a version 4 UUID?
A 128-bit identifier in which almost every bit is random — six bits are fixed to record the version and variant, and the remaining 122 are drawn at random. That is the variant you almost always want, because it needs no coordination between the machines generating it.
Could two UUIDs ever collide?
In principle yes, in practice no. With 122 random bits, you would need to generate around 2.7 quintillion UUIDs before reaching a one-in-a-billion chance of a single collision. It is the kind of probability that is not worth engineering around — you will lose the data to something else long before you lose it to a UUID collision.
Are these random enough to be secure?
They come from the browser's crypto.getRandomValues, which is a cryptographically secure source rather than the ordinary Math.random. That said, do not use a UUID as a security token by itself. It is an identifier, not a secret, and its purpose is uniqueness rather than unguessability.
Should I use a UUID as a database primary key?
It is a genuine trade-off. UUIDs let any client generate an ID without asking the database, which is invaluable in distributed systems and offline-capable apps. The cost is that a random UUID has no natural ordering, so inserts scatter across a B-tree index rather than appending neatly to the end, which fragments the index and hurts write performance at scale. If that matters, look at UUIDv7 or ULID, which put a timestamp in the high bits and are therefore sortable.

Unique without asking anyone

The problem UUIDs solve is coordination. A traditional auto-incrementing database ID requires a single authority to hand out the next number, which works beautifully until you have several databases, or a mobile client that must create records while offline, or a distributed system where no one node is in charge. UUIDs sidestep the whole difficulty by making the identifier space so vast that any participant can simply pick a random one and be confident, to an overwhelming degree, that nobody else has ever picked the same one. No central authority, no round trip, no locking. That property — generate an ID anywhere, at any time, with no coordination — is what makes UUIDs indispensable in modern distributed architectures.

How improbable a collision really is

The numbers are worth internalising, because intuition is badly calibrated here. A version 4 UUID has 122 random bits, giving roughly 5.3 undecillion possible values — a 5.3 followed by 36 zeros. The birthday paradox means collisions become likely far sooner than exhausting that space, and even so, you would need to generate about a billion UUIDs per second for roughly 85 years to reach a 50 percent chance of a single collision. Put differently: if every person on earth generated a thousand UUIDs a second for a century, a collision would still be unlikely. This is why engineers treat UUID uniqueness as a practical certainty and spend their worry budget on the failure modes that actually occur, like hardware faults and bad random number generators.

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