A UUID (Universally Unique Identifier) is a 128-bit identifier standardised by RFC 9562. It is designed to be unique across space and time without a central authority. UUIDs are commonly used as database primary keys, API tokens, and session identifiers.

What is the difference between UUID v4 and v7?

UUID v4 is randomly generated with no embedded meaning. UUID v7 embeds a Unix millisecond timestamp in the first 48 bits, making it time-sortable. This is ideal for database primary keys because time-ordered inserts avoid random page splits and maintain index locality.

Is a UUID the same as a GUID?

Yes. GUID (Globally Unique Identifier) is Microsoft's term for the same concept. The format and generation are identical — the names are interchangeable.

Can two UUIDs ever be the same?

Theoretically yes, but the probability is astronomically small. A v4 UUID has 122 random bits — you would need to generate approximately 2.7 quintillion UUIDs before having a 50% chance of a single collision.

UUID Generator — v4 & v7 (Time-Ordered)

Generate UUID v4 (random) and UUID v7 (time-sorted, ordered UUID) online. UUID v7 embeds a Unix timestamp making it perfect for database primary keys — no random page splits. Free bulk UUID generator, no signup required.

UUID Generator — v4 & v7 (Time-Ordered)

What is a UUID?