UUID Generator
Generate one or many random UUID v4 identifiers, with your choice of hyphens and letter case — all in your browser.
No UUIDs yet — click Generate.
How it works
Set a quantity
Drag the slider or type a number from 1 to 100.
Pick a format
Toggle hyphens and letter case to match whatever system will receive the UUIDs.
Copy what you need
Copy an individual UUID, or grab the whole batch at once with Copy all.
What people use a UUID generator for
Random unique IDs come up constantly once you're building anything with data.
Database primary keys
Seeding test data
Request tracing IDs
Naming files without collisions
Distributed systems, no central authority
A few things worth knowing
A UUID (universally unique identifier) is a 128-bit number, almost always written as 32 hex characters split into five hyphenated groups. Version 4 — the kind this tool generates — derives that number from randomness rather than from a timestamp, a MAC address, or a name, which is what makes it safe to generate independently on any number of machines without coordinating with a central server first.
The randomness comes from your browser's crypto.getRandomValues(), the Web Crypto API's cryptographically secure random source — the same kind of randomness used to generate encryption keys, not the weaker Math.random(). With 122 random bits per UUID, the chance of ever generating the same value twice is small enough to treat as zero for any realistic use, which is exactly why UUIDs are trusted as unique identifiers across databases, distributed systems, and file names without checking for collisions.
The format toggles exist because not every system agrees on how a UUID should look. Some expect the standard hyphenated, lowercase form; others store it as a bare 32-character hex string or expect uppercase letters. Switching those here saves a manual find-and-replace once you've generated a batch.
Frequently asked questions
What is a UUID v4?
A UUID (universally unique identifier) is a 128-bit value formatted as 32 hex characters split into five groups by hyphens. Version 4 means it's generated from random bits rather than derived from a timestamp or a name — two of its bits are fixed to mark it as version 4, and the rest come from a cryptographically secure random source, which is why collisions are astronomically unlikely.
How random are the UUIDs this tool generates?
They're generated using your browser's crypto.getRandomValues(), the same cryptographically secure random number source used for things like generating encryption keys — not Math.random(), which isn't designed to be unpredictable. That's what version 4 of the UUID spec requires for its randomness guarantees to hold.
Can two UUIDs generated by this tool collide?
In practice, no. A version-4 UUID has 122 random bits, giving roughly 5.3 x 10^36 possible values. You'd need to generate billions of UUIDs per second for billions of years before the odds of a single collision became meaningful — that's why UUIDs are trusted as unique identifiers without checking a central database.
Why would I generate UUIDs without hyphens or in uppercase?
Different systems expect different formats. Some databases and APIs store UUIDs as a plain 32-character hex string without separators; some legacy systems or generated code expect uppercase hex. The format options here let you match whatever your target system needs without a separate find-and-replace step.
Why is bulk generation capped at 100?
100 covers realistic one-off needs — seeding test data, generating a batch of keys — without turning the page into an unbounded text dump. If you need thousands, generating in a script with a UUID library is the better tool for that job anyway.
Is this UUID generator free to use?
Yes, completely free, with no account, no sign-up, and everything generated locally in your browser.