The physical compatibility of Subscriber Identity Modules (SIM cards) between Android and iPhone devices is dependent on the SIM card size. Modern smartphones, including both Android and iPhones, primarily utilize Nano-SIM cards. If both devices use the same SIM card size, the card can be physically inserted into the other device.
However, simply inserting a SIM card from one type of phone into another does not guarantee full functionality. The SIM card stores subscriber information and network authentication data, enabling the phone to connect to the cellular network. The phone’s operating system (Android or iOS) and carrier settings must also be compatible to enable features like data, text messaging, and voice calls.