About UUID version 4
A UUID (universally unique identifier) is a 128-bit value written as 32 hex digits in five groups, like 3f8e2a1c-9b4d-4e6f-a2c8-1d5e7f9a0b3c. Version 4 sets 6 bits to mark the version and variant and fills the other 122 with random data, so you can create IDs anywhere without coordination and never expect a collision.
To put that in numbers: you would need to generate about 2.7 quintillion UUIDs before the chance of a single duplicate reached 50 percent.
Identifiers, not secrets
UUIDs often appear in URLs and logs. A v4 UUID is hard to guess, but it is not designed to be a password or access token. For anything that grants access, use the API key or random token generator.
Frequently asked questions
What is the difference between UUID v4 and v7?
v4 is fully random. v7 starts with a timestamp, so values sort in creation order, which keeps database indexes fast. Use the UUID v7 generator for primary keys.
Are GUIDs and UUIDs the same thing?
Yes. GUID is Microsoft’s name for the same 128-bit format. Turn on uppercase and braces to get the {XXXXXXXX-…} style used in Windows and .NET.