UUID Generator

UUID v1 is generated using the current timestamp and the MAC address of the machine. Because it embeds time and node information, two v1 UUIDs generated at different times on the same machine will be monotonically ordered. However, it leaks your machine's MAC address, which can be a privacy concern in some contexts.

UUID v4 is generated using random or pseudo-random numbers. It is the most widely used UUID version due to its simplicity and the near-zero probability of collision. With 122 bits of randomness, the chance of generating two identical v4 UUIDs is astronomically small. Ideal for most use cases where you need a unique identifier without any structured meaning.

UUID v6 is a field-compatible rearrangement of UUID v1. It places the timestamp fields in a monotonically increasing order, making v6 UUIDs sortable as strings while retaining the same information as v1. This makes it more suitable for database primary keys where sortability improves index performance.

UUID v7 uses a Unix millisecond timestamp as the most significant bits, followed by random bits. This results in UUIDs that are naturally sortable by creation time — useful for distributed systems and databases. Unlike v6, v7 is based on a widely understood epoch (Unix time) rather than the Gregorian calendar epoch used by v1/v6.

The NIL UUID is a special form consisting entirely of zeros: 00000000-0000-0000-0000-000000000000. It is defined in RFC 4122 and is used as a sentinel or placeholder value — for example, to represent the absence of a UUID, an uninitialized state, or a root/null entity in a hierarchy.

The MAX UUID is the counterpart to NIL, consisting entirely of ones (0xFFFFFFFF...): ffffffff-ffff-ffff-ffff-ffffffffffff. It was introduced in RFC 9562 and is used as an upper-bound sentinel value. Useful in range queries or as a placeholder representing the maximum possible UUID value.