UUID Generator

A UUID (Universally Unique Identifier), also called a GUID (Globally Unique Identifier on Windows platforms), is a 128-bit label defined by RFC 4122. It is represented as 32 hexadecimal digits split into five groups by hyphens: xxxxxxxx-xxxx-Mxxx-Nxxx-xxxxxxxxxxxx, where M encodes the version and N encodes the variant.

The probability of generating a duplicate UUID v4 is astronomically low — you would need to generate about 1 billion UUIDs per second for 85 years before even a 50% chance of a single collision. In practice, UUIDs are treated as globally unique.

• UUID v4 (random) — generated entirely from random or pseudo-random numbers. The most widely used version. Opaque: reveals nothing about when or where it was generated. The right default for most applications.
• UUID v1 (time + MAC address) — encodes the current timestamp and the MAC address of the generating machine. Our generator uses random bytes for the node field (multicast bit set per RFC 4122) so no real MAC address is exposed.
• UUID v7 (Unix timestamp + random) — introduced in RFC 9562 (2024). Embeds a millisecond-precision Unix timestamp, making v7 UUIDs naturally sortable by creation time. Use v7 as the primary key in databases where time-ordering matters for performance (B-tree indexes stay hot on recent rows).

UUIDs are the right choice when:

• Records are created across distributed systems and you need unique IDs without a central coordinator.
• You want to avoid sequential IDs that expose row counts or creation order to clients.
• IDs must be shareable in URLs or API responses without leaking system structure.
• You're merging data from multiple sources and need namespace isolation.

Sequential integers still win for single-server databases where performance and readability are the top priorities. For distributed systems, v7 UUIDs give you both global uniqueness and database-friendly sortability.