What Is a UID (Unique Identifier)?

A UID (unique identifier) is a string of characters - digits, letters, or both - guaranteed to identify exactly one entity within a defined scope, with no duplicates. The entity can be anything that needs telling apart: a database record, a device, a vehicle, a person, a piece of equipment. The guarantee is the point: when a system trusts that one UID maps to one thing, lookups, transfers, and histories stay unambiguous. Familiar examples include the VIN on a vehicle and the IMEI on a phone.

What makes an identifier unique

Three properties do the work. First, uniqueness within a scope: every UID is unique somewhere - a payroll number within one company, a VIN worldwide. Knowing the scope tells you how far the guarantee travels. Second, immutability: the UID never changes for the life of the entity, even when its name, owner, or location does - that stability is what lets records accumulate against it. Third, no reuse: once an entity is gone, its UID is retired with it, so old history can never be misread as belonging to something new.

Uniqueness is enforced in one of two ways: a central issuer hands out values from a controlled sequence (serial numbers, employee IDs), or the value is generated from such a large random space that collisions are practically impossible (UUIDs).

Common UID examples

• UUID / GUID - the 128-bit identifiers software generates for database rows, files, and sessions.
• VIN - the 17-character code identifying every road vehicle worldwide.
• IMEI - the identity of a mobile handset, independent of its SIM.
• MAC address - the factory-assigned identifier of a network interface.
• ISBN - one number per edition of a book.
• Asset IDs - the identifiers an organisation assigns to its own equipment.

Government use goes further: the US Department of Defense’s IUID programme requires qualifying equipment to carry a permanent, machine-readable unique identifier - typically a Data Matrix mark etched or printed onto the item - so parts remain traceable across decades and contractors.

UID vs serial number vs asset ID

These three get conflated because all are “the number on the device”. The serial number is the manufacturer’s UID - unique within their production line, but possibly duplicated across brands, and often long and awkward to read. The asset ID is your UID - short, consistent in format, unique across everything your organisation owns regardless of manufacturer. A well-kept register records both: the asset ID as the everyday key, the serial for warranty claims, insurance, and theft reports.

UIDs in asset management

Equipment tracking is essentially the discipline of assigning a UID to every item and routing all events through it. That matters most where items are physically identical - a wall of matching security cameras or a kitchen full of identical appliances can only be told apart by their IDs. The habits that keep the scheme healthy: keep IDs short and sequential with a type prefix (CAM-0014), avoid encoding meaning that goes stale (locations, owners), never reuse a retired ID, and put the UID on the item itself as a scannable QR code with the value printed beneath it. In AMPthilly, each asset carries its own internal ID alongside the manufacturer’s serial number, and the QR label generated from the record encodes that identity so a phone-camera scan lands on the right profile.

Related terms

• VIN (Vehicle Identification Number) - the global UID scheme for road vehicles
• IMEI - the UID of a mobile handset
• MAC Address - the UID burned into network hardware
• Asset Marking - putting the UID physically on the item
• QR Code - the scannable format most asset UIDs are printed as