UUID Generator

UUIDs are 128-bit identifiers written as 32 lowercase hex characters in five groups separated by hyphens: `xxxxxxxx-xxxx-Mxxx-Nxxx-xxxxxxxxxxxx`. The `M` nibble encodes the version (4 for random), and `N` encodes the variant (the first bits are `10` for RFC 4122). Everything else is random.

This generator uses the browser's `crypto.randomUUID()`, which delegates to the platform's cryptographically secure random number generator. The collision probability for v4 UUIDs is so small that you would need to generate roughly 2^61 of them to have a 50% chance of seeing one collision — in practice, you will never see one.

When should you pick something other than v4? If your UUIDs become primary keys in a write-heavy SQL table, the fully random values scatter across B-tree pages and hurt insert performance. UUIDv7 or ULID embed a timestamp prefix so inserts stay roughly sequential. If you are handing IDs out publicly, v4 is fine — random means attackers cannot guess the next one.