SIM, eSIM vs iSIM: What’s the Difference?


Cellular devices need specific hardware and software components to connect to cellular networks. These components allow the device to identify and attach to networks owned by specific carriers, enable the network to authenticate the device to ensure it has access (and what kind of access it has), and associate the device and its network usage with a specific account.

As you explore cellular components, at times you may hear several different terms for components that provide the same core function, such as a SIM, eSIM, and iSIM. The difference between these components could have a significant impact on your device’s functionality, security, and scalability, so it’s important to understand the differences between them.

In this article, we’ll examine each of these components and describe how their differences impact your device.

What is a SIM?

sim card

A SIM is a Subscriber Identity Module. It’s a software component that associates a device with a specific subscriber and identifies the device type to the cellular network, among other things. The SIM stores information such as an International Mobile Subscriber Identity (IMSI), International Mobile Equipment Identity (IMEI), and operator profile.

While a SIM is a software component, when people say “SIM,” they’re generally referring to the physical hardware that stores it: a SIM card. This is usually the case when comparing a SIM, eSIM, and iSIM.

SIM cards require a slot in the device. They’re removable, which allows someone to reuse their SIM card in another device or install a new card to access different networks. Over the years, they’ve become significantly smaller and gained storage capacity. Each generation of SIM cards represents a distinct “form factor,” and cellular device manufacturers can select from these based on costs, storage needs, and physical space on their device. (Older form factors are generally lower cost, but larger.)

Advantages of a SIM

The main advantage of using traditional physical SIM cards is that they’re easy to install and if necessary, remove. You simply insert them into their designated slot. They’re also more affordable than newer SIM technologies like the eSIM or iSIM.

Disadvantages of a SIM

Physical SIM cards have several disadvantages. First of all, the fact that they’re removable makes them vulnerable to theft. In fact, identity thieves frequently target SIM cards, removing and using them on other devices.

The slots SIM cards are designed for also make them more vulnerable to the elements, as dust and debris can get in the slot and the SIM card doesn’t have total protection from extreme temperatures, electric shock, or vibrations.

In cellular IoT, one of the biggest disadvantages of traditional SIM cards is that they have to be preloaded with an operator profile (or with Multi-IMSI, multiple operator profiles), and if your connectivity provider no longer works with a particular carrier, the carrier goes out of business, or the device needs to move to another country, you have to physically swap out the SIM cards. If you need to deploy to a new country, you may need to create a whole new SKU for the same product to distinguish between the devices that have different SIMs (to enable them to connect to different operators).

All of these problems can be mitigated by using either an eSIM or iSIM.

What is an eSIM?


An eSIM is an Embedded Subscriber Identity Module. The eSIM standard was first released in 2016, and as SIM card manufacturers raced to offer the latest technology, some ambiguity developed around what “eSIM” actually referred to. Technically, an Embedded Subscriber Identity Module is a specific SIM form factor.

The MFF2 was the first form factor that could be soldered directly onto a cellular device’s circuit board. But eSIMs also came with an advanced new capability: they can switch carriers Over-the-Air (OTA). The technology that enables this is the Embedded Universal Integrated Circuit Card (eUICC), and sometimes this is what people are referring to when they say, “eSIM.” To make matters more confusing, an eUICC can actually be installed on any SIM form factor. So depending on context, someone may use eSIM to refer to a SIM that’s embedded in a device, or to a SIM that can switch carriers OTA because it has an eUICC.

Advantages of an eSIM

eSIMs have several key advantages over traditional SIM cards. First and foremost, they can be provisioned with a new operator profile OTA, which enables you to deploy your device anywhere in the world and you’ll never have to physically swap out the SIM card. This vastly improves your device’s scalability and ensures that your SIM lasts as long as your device.

Since an embedded SIM gets soldered directly onto the device’s circuit board, it has far better protection from potential damage and theft. Safe inside your device, it can withstand more extreme temperatures, shock, vibrations, and dust.

Since it’s significantly smaller than a nano SIM card, an eSIM gives manufacturers far more flexibility when it comes to the design of their devices. You can build smaller devices without worrying about where to include a SIM card slot or how much space to allow for it.

Disadvantages of an eSIM

The main disadvantage of an eSIM is cost. As one of the newest, most advanced SIM technologies, eSIMs are more expensive than traditional SIM cards, and they’re also more complex to install.

What is an iSIM?


An iSIM is an Integrated Subscriber Identity Module. It’s essentially a more advanced eSIM. It provides the same functionality, but you don’t have to solder it onto the device’s circuit board. Instead, an iSIM has a dedicated space on the System of Chip (SoC), where it’s protected by a Tamper Resistant Element (TRE).

Integrated SIMs continue the tradition of making cellular components smaller and more efficient, and it’s just a fraction of the size of an MFF2 (eSIM), which was already substantially smaller than a traditional SIM card. 

Advantages of an iSIM

An iSIM has the same advantages as an eSIM: it’s more durable and tamper-proof, it can change carriers OTA (thanks to its eUICC), and since it’s even smaller than an eSIM and built right into the SoC, it has virtually no impact on your device’s design.

Since the iSIM is built into the chipset, you don’t actually even have to install it. No soldering necessary. At scale, this can help you manufacture and deploy devices faster.

Disadvantages of an iSIM

Currently, iSIMs aren’t in widespread use. This is the newest SIM technology on the market, and so the components (and any components that need to be compatible with them) are significantly more expensive.

Difference between SIM, eSIM, and iSIM

The most obvious difference between the SIM, eSIM, and iSIM is size. Smaller SIM formats give you greater flexibility when it comes to designing your device, and in some applications, building smaller, more discrete devices may be essential (such as surveillance or healthcare).

sim vs esim vs isim

Additionally, eSIMs and iSIMs are always going to cost more than traditional SIM cards. They’re more complex and advanced, which makes them more expensive to produce and develop with. However, this upfront cost can save you the monumental cost (or disruption to your business) of having to physically replace SIM cards down the road.

Get the SIMs you need with emnify

While the iSIM hasn’t been implemented at scale yet, IoT manufacturers still have a range of options when it comes to SIM form factors. emnify’s global IoT SIMs are available in all traditional form factors and the MFF2, and you can add eSIM capabilities to any of them. These network agnostic SIMs enable your devices to connect to more than 540 networks in over 190 countries.

We’ll even send you test SIMs for free. Request an evaluation pack, and we’ll send you two of our SIMs in the form factor of your choice with prepaid data plans and 60 days of access to our connectivity platform.

Get your free SIMs.

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