UUID Generator - Version 4, Free, Local
Generate random version 4 UUIDs (universally unique identifiers), one at a time or dozens at once, using your browser's cryptographic random number generator.
Maintained by Hirantha Sandaruwan Lakshan. Updated 31 July 2026.
How it works
A version 4 UUID is 122 bits of randomness formatted into the standard 8-4-4-4-12 hyphenated layout, with a few fixed bits marking it as version 4 and its variant.
The randomness comes from crypto.randomUUID(), a browser-native method built on the same cryptographically secure random source used elsewhere in the Web Crypto API, not a predictable pseudo-random function.
With 122 random bits, the chance of two independently generated version 4 UUIDs colliding is negligible even across billions of IDs, which is why they're commonly used as database primary keys and unique identifiers.
Worked examples
Generating a primary key for a new database row
Copy a single UUID to use as a unique identifier in a script, seed file, or manual database entry.
Generating test data in bulk
Set the quantity to generate dozens of UUIDs at once and copy them all for use as placeholder IDs in test fixtures.
Creating a unique session or request ID
Generate a UUID to use as a one-off identifier for tracing a request or session in logs.
Frequently asked questions
Is my generated UUID sent anywhere?
No, UUIDs are generated entirely in your browser tab.
How likely is a collision between two UUIDs?
Vanishingly unlikely - version 4 UUIDs have 122 random bits, so generating billions of them still carries negligible collision risk.
Can I generate more than one at a time?
Yes, set the quantity to generate a batch and copy them all together.
What's the difference between UUID and GUID?
They're effectively the same concept - GUID is Microsoft's term for the same kind of identifier defined by the UUID standard.
Are UUIDs random or sequential?
The version generated here is random. That makes collisions vanishingly unlikely, but it also means UUIDs don't sort chronologically the way an auto-incrementing ID does.
Can I use a UUID as a database primary key?
Yes, and it's common. The trade-off is that random UUIDs scatter writes across an index, which can hurt insert performance on very large tables compared with sequential keys.
Is a UUID safe to expose publicly?
Yes, in the sense that it can't be guessed. It isn't a secret or an access token though - never rely on a UUID being unguessable as your only protection.
Are UUIDs guaranteed to be unique?
Not mathematically guaranteed, but the probability of a collision is so small it can be treated as impossible for any realistic number of IDs.
Sources & references
Updated Jul 31, 2026