How UUID Generator Works
Each UUID follows the version 4 format: 32 hex digits arranged as xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx, where the version nibble is fixed at 4 and the variant nibble is fixed to indicate the standard variant. Every other digit is generated using your browser's crypto.getRandomValues() — a cryptographically secure random number source — rather than Math.random().
How to Use This Tool
- Set how many UUIDs you want (up to 200 at once).
- Pick lowercase or UPPERCASE formatting.
- Select Generate.
- Copy all of them at once, or download them as a text file.
Example
A generated UUID v4 looks like 3fa85f64-5717-4562-b3fc-2c963f66afa6 — the 4 right after the second hyphen marks it as version 4, and the character right after the third hyphen is always 8, 9, a or b.
Helpful Tips
- UUID v4 identifiers are effectively unique — the odds of two random ones colliding are astronomically small, which is why they're commonly used as database keys and object IDs.
- Generating 200 at once is handy for seeding test data or fixtures.
Frequently Asked Questions
Are these UUIDs guaranteed to be unique?
UUID v4 relies on randomness rather than a central authority, so uniqueness isn't mathematically guaranteed — but with 122 random bits, collisions are practically impossible.
Why does it use crypto.getRandomValues() instead of Math.random()?
Math.random() isn't guaranteed to be cryptographically secure or unpredictable. crypto.getRandomValues() uses your operating system's secure random number source, which is the recommended approach for generating identifiers.
Are the generated UUIDs sent anywhere?
No, they're generated and stay entirely in your browser.
This tool runs entirely in your browser. Your input is not uploaded to any server.