A UICC is a "smart card" that can work with LTE and 3G and 4G cellular devices. It has a variety of uses but is most frequently used as a SIM card in cell phones. ICCs (Integrated Circuit Cards), which were utilized with 2G and early 3G devices, have largely been supplanted by UICCs.

A UICC is a minuscule card with an embedded chip that is no larger than a miniature. A CPU, non-volatile memory (NVRAM), ROM, and RAM are all present in this device. A gadget on a cellular network can be identified using the special number on each card. Additionally, the device might keep information like user-saved contacts. Although UICCs don't have a set amount of storage, they typically have at least 256 kilobytes and sometimes even more than one gigabit.

UICCs are referred to as "universal" because a single card can handle numerous apps and consequently numerous cellular networks. Examples include ISIM (IP Multimedia Services Identity Module) for UMTS networks, CDMA networks' CSIM (CDMA Subscriber Identity Module), and GSM networks' USIM (Universal Subscriber Identity Module). UICCs can function with a variety of cell networks worldwide due to their universality.

A UICC must have its unique identity (ICC ID) registered and enabled with a mobile service provider in order to be used. A smartphone or other cellular device becomes unrecognisable on the network when the card is removed. The UICC card will typically be instantly detected and useable on the network if you put it into another device.