Why Apple maxes out at two active SIM/eSIMs on its hardware

Why can't your iPhone or iPad have three active cellular network IDs simultaneously—two eSIMs and one physical SIM, or three eSIMs? It's not a deliberate attempt by Apple to frustrate users; rather, it's a hardware constraint based on their assessment of typical user needs.

While some iPads and iPhones possess the hardware to handle two (iPad) or three (iPhone) cellular subscriptions concurrently, their architecture only permits one (iPad) or two (iPhone) to be active at any given time. Newer US iPhone models are even more limited, featuring circuitry for only two active subscriptions.

Let's examine the details.

Understanding SIMs and eSIMs

A SIM (Subscriber Identity Module) is how a cellular device identifies itself to a network. It's essentially an ID linked to a billing account. The evolution of SIMs from the larger Mini SIM to the smaller Nano SIM reflects a trend toward miniaturization.

An eSIM (embedded SIM) eliminates the physical SIM card, integrating the necessary circuitry directly into the device. Apple and others use software to program the eSIM with subscriber details. eSIMs offer convenience for travelers, eliminating the need for physical SIM swaps. Apple introduced eSIMs in the iPhone XS, XS Max, and XR, and later in various iPad models.

Hardware Limitations

The number of simultaneously usable SIMs/eSIMs is a hardware limitation, not a software restriction:

• Dual eSIM iPhones: These devices have two eSIM modules.
• SIM eSIM iPhones: These have a SIM card slot and one eSIM module.
• iPads and certain iPhones: While capable of handling multiple SIM profiles, the hardware routing only allows one active SIM signal at a time. This design choice likely reflects a cost-benefit analysis by Apple, especially considering their shift towards eSIM-only iPhones in the US.

As eSIM adoption grows, Apple will likely eliminate the physical SIM slot from all iPhones and iPads globally, mirroring their removal of the headphone jack.

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