What is iSIM and how does it work? When will Apple bring iSIM to the iPhone?

Learn about the latest SIM technology standard, the Integrated Subscriber Identification Module, or iSIM, and when Apple might release an iPhone with one.

Illustration depicting ejecting a SIM card from an iPhone

The SIM evolution so far

Subscriber Identity Module, Subscriber Identification Module, or simply SIM, enables your iPhone to use cellular networks. A tiny chip on a plastic card securely stores the international mobile subscriber identity (IMSI) number and related key, which are required to identify your device on a mobile phone network.

The first SIM card was developed by German smart card maker Giesecke & Devrient in 1991. Since then, the SIM card standard has undergone several iterations that have shrunk its size while introducing new features.

The iPhone has supported standard SIM cards, their smaller Micro SIM and Nano SIM variants, and eSIM—but there’s already the next generation of SIM, dubbed iSIM.

What is iSIM? How does it work?

Nano SIM card tray set against a gradient gold background
This is a Nano SIM card tray | Image: Christian Zibreg/iDB

Integrated Subscriber Identity Module (iSIM) puts a SIM chip directly into the phone’s application processor. So instead of an eUICC chip permanently attached to a phone (eSIM), the SIM card’s functions are now integrated into a secure enclave of the main chipset that powers the phone (iSIM).

The main benefits of this approach are better dust and water resistance, reduced costs, better security and vastly improved power efficiency. As it’s roughly a hundred times smaller than a physical Nano SIM card, which measures 12.3 x 8.8mm, iSIM technology frees up valuable space inside a mobile device for other hardware features such as better cameras, additional sensors or larger batteries.

To give you a ballpark idea, an iSIM takes up less than one square millimeter.

First Integrated SIMs were introduced by Deutsche Telekom in 2021 as an alternative to eSIM for tiny, low-powered Internet of Things accessories, but it was the fabless semiconductor maker ARM that designed iSIM technology in 2018.

iSIM is now coming to the fore, with flagship Android smartphones such as future Samsung Galaxy devices expected to adopt iSIM technology in 2023 and 2024.

That’s because Qualcomm, which supplies much of the Android world with processors, at Mobile World Congress in February 2023 unveiled a special version of its Snapdragon 8 Gen 2 chipset that incorporates iSIM.

When will the iPhone adopt iSIM?

Considering iSIM is a new technology, it would be reasonable to expect this year’s iPhone 15 family to adopt eSIM or the iPhone 16 models arriving in 2024. We expect Apple to integrate iSIM functionality into future iPhone silicon (A17 or A18).

iSIM could also be built directly into custom wireless chips that Apple is rumored to have been developing for years. The most recent rumors indicate that the company might bring its first iPhone with an in-house designed cellular modem in 2024.

The Cupertino company is also thought to be working on its own chip for Wi-Fi and Bluetooth functionality. A custom 5G modem and Wi-Fi/Bluetooth chipsets would be suitable candidates to integrate the functions of the SIM card via iSIM.

The iPhone 14 goes all-in on eSIM

convert physical sim to esim
Converting a physical SIM into an eSIM | Image: Ankur Thakur/iDB

The iPhone 14, iPhone 14 Plus, iPhone 14 Pro and iPhone 14 Pro Max models hit store shelves in September 2022 as the first Apple smartphones without a SIM card tray. That’s because all models in the iPhone 14 lineup contain a programmable SIM chip, or eSIM, embedded directly into the device’s logic board.

All iPhone 14 units offered in the US support eSIM exclusively, so they have no tray for a physical SIM card. Units sold outside the US have both eSIM and a SIM card tray, except iPhones sold in mainland China that don’t support eSIM.

But the iPhone 14 and iPhone 14 Pro aren’t Apple’s first phones that support eSIM—those would be the iPhone XS, iPhone XS Max and iPhone XR. Apple actually unveiled its first device with eSIM support a year earlier—the Apple Watch Series 3. The first iPad to support eSIM is the third-generation iPad Pro, announced in 2018.

Helpful iPhone SIM tutorials