UUID Generator

A UUID (Universally Unique Identifier) is a 128-bit value written as 32 hex digits in five groups, used to label things uniquely without a central authority.

A v4 UUID is generated from random data. The chance of two colliding is astronomically small, which is why it is the most common choice for IDs.

Yes. They are generated from a cryptographically secure random source on the server.

A v4 UUID is fully random, while a v7 UUID embeds a Unix timestamp in its leading bits so values sort in roughly chronological order. Time-ordered v7 identifiers are friendlier to database indexes.

Random v4 values scatter inserts across an index, which fragments it, whereas v7 values that increase over time are appended in order, reducing index churn and improving write performance.

Not absolutely, but the probability of a collision for random v4 UUIDs is so vanishingly small that they are treated as unique in practice, even across independent systems generating them without coordination.

A random v4 UUID has enough entropy to be hard to guess, but a v7 UUID leaks a timestamp and is more predictable. For security tokens prefer a dedicated cryptographically random value rather than relying on UUID structure.