The compatibility of Subscriber Identity Module (SIM) cards between Android and iPhone devices is generally seamless. SIM cards store information that identifies and authenticates a mobile subscriber, enabling access to a cellular network. Because both Android phones and iPhones adhere to industry standards for SIM card sizes (Nano-SIM being the most prevalent in modern devices), a SIM card from one type of phone can physically fit into the other type.
This interchangeability stems from the industry-wide adoption of SIM card standards. These standards ensure that the electrical interface and communication protocols between the SIM card and the mobile device are consistent, regardless of the operating system. Therefore, users benefit from the ability to switch their cellular service between different devices without needing a new SIM card, so long as the devices are unlocked.