In theory yes, in practice no. UUID v4 has 122 random bits, putting the collision probability around 1 in 5.3×10³⁶ — you would need to generate billions of UUIDs per second for decades to have a meaningful chance of a single duplicate. For any real application, treat them as unique.

Version 4 UUIDs are generated almost entirely from random data — unlike version 1, which embeds your machine's MAC address and a timestamp. That makes v4 both simpler and more private: nothing in the identifier reveals when or where it was created.

Yes. This tool uses the Web Crypto API (crypto.randomUUID / crypto.getRandomValues), which draws randomness from your operating system's secure entropy source — the same quality of randomness a server would use. It does not use the predictable Math.random().

RFC 4122 specifies lowercase as the canonical output format, but UUIDs are defined to be case-insensitive for comparison. Use whichever your database or style guide prefers — just be consistent, and compare case-insensitively if sources mix.

Use UUIDs when IDs are generated on multiple machines or clients that can't coordinate (distributed systems, offline-first apps), or when you don't want IDs to be guessable or reveal record counts. Auto-increment integers remain smaller, faster to index, and perfectly fine for a single-database app.