What Is an iSIM? Integrated SIM vs eSIM Explained

An iSIM (integrated SIM) builds SIM functionality directly into a device's main processor instead of a separate eSIM chip. It does the same job as a SIM card or an eSIM: it identifies the device to a mobile network. Like an eSIM, it receives its plan remotely instead of from a card. So far, iSIM announcements have centred on chips and connected (IoT) devices rather than named phone models.

This guide explains what an iSIM is, how it differs from an eSIM, where it is used today, and what it means if you use a travel eSIM.

What does iSIM stand for?

iSIM stands for integrated SIM. "Integrated" refers to where it lives: inside the device's system-on-chip (SoC), the main processor that also runs the device itself. In industry documents you may also see the terms iUICC or ieUICC for the same idea.

Don't confuse it with IBM ISIM, an identity-management software product that shares the name but has nothing to do with mobile networks.

How does an iSIM work?

• A protected area inside the processor holds the SIM. Instead of a separate chip, the SIM software and its security keys sit in a tamper-resistant section of the main processor.

• It proves who you are to the network, like any SIM. The iSIM answers the network's identity check the same way a SIM card or eSIM does. For the step-by-step version, see how a SIM card works.

• Plans are downloaded, not inserted. The first commercially certified iSIM, announced by Thales and Qualcomm in 2023, is described as fully compliant with the GSMA Remote SIM Provisioning standard, the same family of standards that lets eSIMs download plans.

SIM vs eSIM vs iSIM

For a closer look at the first two columns, see our eSIM vs physical SIM comparison.

eSIM vs iSIM: what's actually different?

For the person using the device, very little. Both are built in, can't be removed and get their plans over the air. The differences matter mostly to the companies that make devices:

• Location. An eSIM is its own small chip. An iSIM has no chip of its own; it is part of the processor.

• Space and parts. Removing the separate SIM component frees up room inside the device and removes a part that has to be bought and fitted.

• Power. Vendors say iSIMs use less power. Kigen, which makes iSIM software, claims up to 70% less power; that figure comes from the vendor and hasn't been independently tested.

If you want the basics of the technology iSIM builds on, start with what an eSIM is and how it works.

Where are iSIMs used today?

Most commercial iSIM activity so far is in IoT: small connected devices such as trackers and sensors, where saving space and battery matters most. In January 2025, for example, Soracom announced commercial availability of its iSIM together with an iSIM-compatible module from Murata, aimed at low-power IoT devices and built with Sony Semiconductor Israel and Kigen.

iSIM milestones

Looking ahead, the 2023 Thales and Qualcomm announcement quoted a forecast from Kaleido Intelligence of around 300 million iSIM shipments by 2027, about 19% of eSIM shipments. That is a forecast, not a measured figure.

Limits and open questions

• Adoption depends on others. Chip support alone doesn't put an iSIM in your hands; device makers and carriers both have to support it.

• It is tied to the processor. As with an eSIM, there is no card to move to a spare device if the hardware fails; the plan has to be reissued.

• Most claims come from vendors. Figures on power and cost savings are published by companies that sell iSIM technology, so treat them as claims until independent tests appear.

Does your phone have an iSIM?

Probably not in a way you would notice. A chip that supports iSIM is not the same as a phone that uses it: the phone maker has to switch it on, and carriers have to support it. The 2023 certification announcement for the Snapdragon 8 Gen 2 named no phone model and no launch date.

What matters for you is whether your phone can add an eSIM. You can check that on our supported devices page.

What does iSIM mean for travelers?

Nothing changes today. Travel eSIMs install on any phone that supports eSIM and is unlocked. If phones with an active iSIM do arrive, they follow the same GSMA remote provisioning standard, so downloadable travel plans should install in much the same way.

Heading abroad? Browse eSIM70