Why can’t you have three cellular network IDs on your iPhone or iPad active at once–two eSIMs and one SIM or three eSIMs? Or even more? You might think Apple is trying to frustrate you. But it’s a hardware limitation that’s designed around what Apple thinks represents the vast majority of its users’ needs. The short answer is that Apple has the necessary hardware built into some iPads and iPhones could allow two (iPad) or three (iPhone) cellular subscriptions

The SIM (Subscriber Identity Module) is a way for a device with cellular capability to identify itself to any compatible network nearby. It’s essentially an ID connected to a billing account. When a cellular phone, watch, or other device connects to a cell network base station, the SIM serves as a unique identifier that allows the operator of that base station to check for active service–all in a split
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