what is a uid

A UID, or unique identifier, is a string of characters or numbers that is associated with a single entity within a given system. The purpose of a UID is to distinguish that entity from all other entities in the system, making it possible to address and interact with it. UIDs can be assigned to anything that needs to be distinguished from other entities, such as individual users, companies, machines, or websites. There are many ways to generate UIDs, including hash functions, random number generators, and names or codes allocated by choice which are forced to be unique by keeping a central registry. UIDs are used in a variety of contexts, including physical supply chains, where manufacturers often mark individual pieces of a larger component with a serial number to trace back the origin of the product in case of a malfunction, defect, or recall. The Department of Defense (DOD) also requires UIDs for all equipment with an acquisition cost exceeding $5,000, as well as mission-critical equipment, controlled inventory, serially-controlled equipment, and consumable equipment. The DOD has mandated that all federal contractors have UID markings on government-furnished military and non-military equipment, and items are not eligible for IUID registry until they have UID markings with unique item identifiers.