The central question concerns the compatibility of subscriber identity module (SIM) cards between devices operating on different mobile operating systems, specifically Android and iOS. A SIM card stores information that identifies a mobile subscriber to a cellular network. These cards are typically interchangeable physically; however, certain factors determine whether a card utilized in an Android device will function correctly in an iPhone.
The primary consideration revolves around network locking and SIM card size. If an Android device is locked to a specific carrier, the SIM card used within it may not function in an iPhone without unlocking. Furthermore, SIM card sizes have evolved over time; newer iPhones typically use nano-SIM cards, while older Android devices may use micro-SIM or even standard SIM cards. A physical adapter is necessary if the SIM card from an older Android device is larger than the nano-SIM slot in a modern iPhone.