[#introduction]
= Introduction

:idprefix: introduction_

A UUID, or universally unique identifier, is intended to uniquely identify information in a distributed environment without significant central coordination.
It can be used to tag objects with very short lifetimes, or to reliably identify very persistent objects across a network.

A formal definition for UUID can be found in https://datatracker.ietf.org/doc/rfc4122/[RFC 4122] and https://datatracker.ietf.org/doc/rfc9562/[RFC 9562].

UUIDs have many applications.
Some examples follow: Databases may use UUIDs to identify rows or records in order to ensure that they are unique across different databases, or for publication/subscription services.
Network messages may be identified with a UUID to ensure that different parts of a message are put back together again.
Distributed computing may use UUIDs to identify a remote procedure call.
Transactions and classes involved in serialization may be identified by UUIDs.
Microsoft's component object model (COM) uses UUIDs to distinguish different software component interfaces.
UUIDs are inserted into documents from Microsoft Office programs.
UUIDs identify audio or video streams in the Advanced Systems Format (ASF).
UUIDs are also a basis for OIDs (object identifiers), and URNs (uniform resource name).

An attractive feature of UUIDs when compared to alternatives is their relative small size, of 128 bits, or 16 bytes.
Another is that the creation of UUIDs does not require a centralized authority.

When UUIDs are generated by one of the defined mechanisms, they are either guaranteed to be unique, different from all other generated UUIDs
(that is, it has never been generated before and it will never be generated again), or it is extremely likely to be unique (depending on the mechanism).
