As the name goes A micro-SIM is a miniaturized alternative to a SIM card for subscriber identification on mobile devices. The physical size of the card is 12mm x 15mm though it is smaller than the mini SIM used in GSM mobile telephony devices, the contact area is identical.

The micro-SIM is identified as Mini-UICC in the ISO 7816 specification.

T-Mobile and Lok8u announced during the 2010 International CES in Las Vegas that they would be the first to bring Micro Third-Form-Factor (3FF) SIM cards to the US Machine-to-Machine (M2M) Market with a line of wearable GPS locator devices.

The micro-SIM format received a major boost when announced as the means of adding third-party 3G connectivity to the Apple iPad. Micro-SIMs have been used for a several years in embedded smart devices, such as power meters.