QoinWhat a UUID is
A UUID (universally unique identifier) is a 128-bit value written as 32 hexadecimal digits in five groups, 8-4-4-4-12, for example 9b2f1c4e-7d3a-4f8b-a1c6-2e5d7f9b0a13. Version 4 UUIDs are random: 6 of the 128 bits mark the version and variant (the 4 at the start of the third group and the 8, 9, a or b at the start of the fourth), the other 122 bits come from a random generator. That leaves about 5.3 × 10³⁶ possible values, so two independently generated UUIDs colliding is not something you plan for: at a billion UUIDs a second it would take about 85 years to reach even a 50 % chance of a single collision.
UUIDs are used as database keys, request and session identifiers, file names and anywhere an id must be unique without a central counter. This page uses the browser's cryptographic random generator, produces lowercase UUIDs per RFC 9562 and keeps everything on your device; nothing is sent or stored.