An iSIM (integrated SIM) is a SIM that's built right into your device's main chip, instead of being a plastic card or a separate eSIM chip. It does the same job as any SIM: it holds the details your carrier uses to connect you to its network. iSIMs are already used in some connected IoT devices, but phones today still use eSIM. This guide explains what iSIMs are, how they compare with SIM cards and eSIMs, which devices use them and what they mean for your next trip.
What are iSIMs? The integrated SIM in plain words
iSIM stands for integrated SIM. You'll also see it written as i-SIM or integrated SIM card, but there's no card at all. The SIM software runs in a protected, tamper-resistant area inside the device's main processor, called the system-on-chip (SoC).
The GSMA, the mobile industry body that writes the eSIM standards, calls this an Integrated eUICC. In its eSIM architecture specification (SGP.21), it defines it as an eUICC "implemented on an Integrated TRE", which is a tamper-resistant element "implemented inside a larger System-on-Chip". Put simply, an iSIM is an eSIM that lives inside the main chip instead of next to it.
That's why an iSIM that follows the GSMA standard works like an eSIM for you: you download a mobile plan to it, you don't insert anything.
iSIM vs eSIM vs SIM card
All three hold the same kind of information. The difference is where it lives and how you get a plan onto it:
- SIM card: a removable plastic card with a chip. You get it from your carrier and put it in your phone's SIM tray. Read more about what a SIM card is.
- eSIM: a small separate chip soldered into your phone. You download plans to it, usually by scanning a QR code. Apple describes it as a digital SIM built into your iPhone. Our guide on what an eSIM is explains how it works.
- iSIM: the same eSIM function, but built into the main processor. There's no separate SIM chip on the circuit board.
For a full side-by-side look at cards and eSIMs, see SIM cards vs eSIM. If you want to know all the SIM sizes and types, read the different types of SIM cards.
What are the benefits of iSIMs?
The benefits mostly matter to the companies that make devices, and they show up for you as smaller or longer-lasting gadgets.
Compact design
With no SIM tray and no separate SIM chip, device makers save space on the circuit board. Altair, which makes cellular IoT chips with an integrated SIM, says on its iSIM FAQ that this lets makers build smaller devices with fewer parts and no SIM tray.
Power efficiency
Altair also says iSIM helps device makers offer more power-efficient devices. That matters most for small connected devices such as trackers and smart meters that have to run on a battery for a long time.
Security
An iSIM can't be pulled out of a lost or stolen device. Altair says the SIM software in its chips runs on an isolated secure element inside the chip. For phones, Thales and Qualcomm say their iSIM is certified by the GSMA.
Flexibility
An iSIM that follows the GSMA remote provisioning standard can download plans over the air, just like an eSIM. That means you could switch carriers or add a travel plan without a new card. Not every iSIM can do this, as you'll see below.
Which phones and devices have an iSIM?
This is the part most articles skip. Here's what is confirmed by the companies involved:
- The first smartphone demo, 2022: Vodafone, Qualcomm and Thales showed iSIM working in a modified test phone. Thales described it as the world's first smartphone demonstration of iSIM technology. It was a demo, not a phone you could buy.
- The first certified iSIM for phones, 2023: Thales and Qualcomm announced the first GSMA-certified iSIM, on Qualcomm's Snapdragon 8 Gen 2 mobile platform, and said it follows the GSMA remote SIM provisioning standard. Qualcomm's announcement didn't name any phone that would ship with it.
- IoT devices: Altair says the integrated SIM in its ALT1250 and ALT1255 IoT modems is commercially deployed and approved by operators including AT&T and LG U+.
So which iSIM phones can you buy? We couldn't find a phone maker that lists iSIM in its official specs. Phones list eSIM, and that's what you set up and use. A chip that can do iSIM doesn't mean the phone uses it: the phone maker and carriers have to switch it on.
The easy way to know what your phone supports is to check for eSIM. Our guide on how to check eSIM compatibility shows you how.
What are the challenges of iSIMs?
Not every iSIM can switch carriers
Some IoT iSIMs follow older ETSI and 3GPP SIM standards, not the GSMA eSIM standard. Altair says that with its current integrated SIM, the operator can't be changed after the first profile is set up. So "iSIM" doesn't always mean "switch carriers whenever you want".
Phone makers and carriers have to adopt it
Phones already have eSIM, and it works. For iSIM to replace it, chip makers, phone makers and carriers all have to support it. Until they do, eSIM is what you'll use.
Local rules
Some countries have rules on how SIMs are registered or personalised. Altair notes that some markets have local rules on SIM personalisation, which iSIM makers have to support.
What iSIM means for your next trip
Right now, nothing changes for you. To use a travel plan, your phone needs eSIM support. A GSMA-standard iSIM uses the same remote provisioning as eSIM, so on your side it would work the same way: you'd scan a QR code or tap a link, the plan downloads, and you turn the line on.
That also means a travel eSIM installs the same way either way. You keep your home SIM for calls and texts and add a data plan for the country you visit:
- Check that your phone supports eSIM and isn't locked to your carrier.
- Pick a plan for your destination.
- Install it before you leave, while you're on Wi-Fi. Our guide on how to install an eSIM walks you through it.
- When you land, switch your mobile data to the travel line and turn on data roaming for it.
If your phone supports eSIM, you can use a travel eSIM today. These data-only plans install before you fly, and your own SIM stays on for calls and texts.
Europe, USA and Asia plans shown · data-only eSIMs, no phone number · Find the eSIM for your destination
FAQ
What does iSIM stand for?
iSIM stands for integrated SIM. The SIM is integrated into the device's main processor instead of being a card or a separate chip.
Is an iSIM the same as an eSIM?
Not quite. Both let you download plans instead of inserting a card. An eSIM is a separate chip in your phone. An iSIM puts the same function inside the main processor. The GSMA treats it as an integrated version of the eSIM chip.
Is an iSIM a SIM card?
No. There's no card or tray. The SIM is part of the device's chip, so you can't remove it or move it to another device by hand.
Which phones have an iSIM?
Qualcomm's Snapdragon 8 Gen 2 platform got the first GSMA-certified iSIM in 2023, but we couldn't find a phone maker that lists iSIM in its official specs. For travel, what matters is whether your phone supports eSIM.
Who provides integrated SIMs?
Chip makers and SIM security companies build them, for example Qualcomm with Thales for phones, and Altair with G+D for IoT modems. Your plan still comes from a mobile carrier or eSIM provider.
Is an iSIM the same as the ISIM app on my SIM?
No. ISIM in capitals is short for IP Multimedia Services Identity Module. It's an application on a SIM or eSIM that your phone uses to access your carrier's IMS services, as defined in the 3GPP ISIM specification. It has nothing to do with the integrated SIM.
Will iSIM replace eSIM?
Nobody can say for sure yet. A GSMA-standard iSIM works with the same remote provisioning as eSIM, so the eSIM plans you buy today use the same system.
Can I use a travel eSIM on a phone with an iSIM?
If the iSIM follows the GSMA remote provisioning standard, you add a travel plan the same way as on any eSIM phone. Always check your phone's eSIM support before you buy.
