UUID Generator (v4)
Generate one or many RFC 4122 version 4 UUIDs using cryptographically secure randomness — entirely in your browser.
How to use this tool
Choose how many UUIDs to generate (up to 500 at once), pick formatting options, then select "Generate". Press "Copy all" to copy every generated UUID to your clipboard, one per line.
About UUID v4
A version 4 UUID is a 128-bit value formatted as 32 hex digits in the pattern xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx, where the "4" marks the version and "y" is one of 8, 9, A, or B (marking the RFC 4122 variant). The remaining 122 bits are random, giving roughly 5.3 × 10³⁶ possible values — collisions are practically impossible even generating billions of UUIDs.
Uses crypto.randomUUID() where available (all current major browsers), or an RFC 4122-compliant fallback built from crypto.getRandomValues() — cryptographically secure randomness either way, not Math.random().
Frequently asked questions
What is a UUID v4?
A Universally Unique Identifier, version 4, is a 128-bit identifier that's almost entirely random (122 random bits, with 6 fixed bits marking the version and variant per RFC 4122). The chance of a collision between two randomly generated v4 UUIDs is astronomically small.
How random are these UUIDs?
This tool uses crypto.randomUUID() where available, or falls back to manually building an RFC 4122-compliant v4 UUID from crypto.getRandomValues() — both are cryptographically secure random sources, not Math.random().
Are generated UUIDs sent anywhere?
No. Generation happens entirely in your browser. Nothing is transmitted, logged, or stored.