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    Dec, 10 2020

    What is an eSIM?

    Quick definition: An eSIM refers to an Embedded Subscriber Identity Module or an Embedded Universal Integrated Circuit Card (eUICC). An eUICC is a component of a SIM card which allows you to change operators Over-the-Air (OTA), whereas an embedded SIM is an actual SIM card that gets soldered directly into a cellular device.

    Last updated: August 22, 2022

    Iot Glossary
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    In smartphones, an embedded SIM always uses an eUICC, which is why you’ll often see these terms used synonymously. But that’s not the case when it comes to the Internet of Things. IoT devices may use embedded SIMs which may or may not be eUICC compatible.

    Traditional SIM cards come in several form factors (mini, micro, nano) and have to be plugged into a device, but an MFF2 SIM is a specialized form factor that fits right on the circuit board. Soldering it to the circuit board protects it from dust, electric shocks, and other environmental hazards. MFF2s are significantly smaller than traditional SIMs, too, which gives manufacturers more room and the ability to create sleeker devices.


    Let’s look at the difference between a consumer eSIM and M2M eSIM, the benefits of using an eSIM, and how eSIMs compare to standard SIMs.

    The difference between a consumer eSIM and M2M eSIM 

    Consumer eSIMs are available in high-end phones like the iPhone, Google Pixel, Samsung S20 or Huawei P40. They are directly soldered within the device. The user can simply select the operator for the eSIM on the phone or by scanning a QR code which directly downloads the new operator profile to the SIM. This “pull” model is quite simple to handle. 

    M2M eUICC/eSIMs are a different breed and need completely different technology. In fact the technology is older than the one for the consumer use case and specially designed for the automotive sector. The M2M eUICC variant requires a more complex infrastructure because you usually don’t have the IoT device in your hands when you want to change the profile, and there is no camera or device agent available that can pull the profile to the device. 

    M2M eUICCs are registered to a specific subscription manager platform component (SM-SR) that is either owned by the automotive manufacturer or by an operator. In case the car manufacturer wants to add or change operators, they need to integrate or migrate the eUICCs over to another platform which requires several months and tens of thousand of Euros to accomplish. 

    However, standardization bodies like GSMA have made progress toward simplifying profile management for the M2M case and come up with a pull model as well.

    Form factors and eSIM

    Standard SIM cards come in several different form factors:

    • 2FF (mini)
    • 3FF (micro)
    • 4FF (nano)
    • MFF2 (embedded SIM)

    M2M eUICCs/eSIM come in the same form factors, but with the advantage of being able to switch the profile associated with them. This means existing IoT devices can still be equipped with the same insertable SIM cards but with the added eUICC functionality.    

    The benefits of using an embedded SIM form factor and eSIM

    There are several key advantages to using an MFF2 instead of the conventional SIM form factors (2FF, 3FF, 4FF). And it’s not just about aesthetics or freeing up a little extra space on your device. 

    Longer lasting functionality

    In addition to being better protected from the elements (because it’s soldered to your device, so the connection pins stay in place better), embedded SIMs actually have a longer lifespan than traditional SIMs. An MFF2 eSIM can last up to 17 years, whereas a traditional SIM may last more like 10 years. For most IoT applications, this means your SIM will likely outlast your device.

    Simplifying SIM logistics

    The idea behind the eUICC/eSIM is to solve some major logistical hurdles that manufacturers and end users have to navigate with a conventional SIM. Especially when you combine an MFF2 with an eUICC.

    Switch between carriers without switching SIMs

    With traditional UICCs, your SIM is only compatible with a specific cellular carrier and their partner networks. If you want to switch carriers, you need to switch SIMs. One of the biggest benefits of an eUICC is the ability to provision a new MNO profile over-the-Air (OTA), enabling you to connect to new cellular networks. 

    Simplified regulatory compliance

    Some countries (like Brazil and India) prohibit cellular devices from permanently roaming. (In Brazil, for example, you can only roam for 90 days.) This means that to be compliant, you can’t just use a carrier that has a roaming agreement with another operator in these countries. If you’re going to deploy there, you need to have a profile that’s associated with a local carrier.

    With an eUICC, you can work with your current carrier and a local operator to provision a new profile to your SIM, so your devices can comply with that country’s telecommunications regulations. 

    Less dependence on carriers

    Normally, when your operator starts charging higher prices, you’re stuck with the increased overhead. You can’t just recall all your devices or send personnel to install new SIMs for every customer. The rates go up, and that’s that. But with an eUICC, you have more options. You can provision a new MNO profile to a more affordable carrier and avoid the increased rates.

    Similarly, if your carrier goes out of business, it doesn’t have to completely disrupt your business. You can provision a new profile and ensure your customers stay connected, even though your old carrier’s network is no longer available

    Lower data costs for new deployments

    Just because you have coverage in a country doesn’t mean it’s cost effective. In applications where your devices use a significant volume of data, such as car entertainment systems, you don’t want to be stuck with a profile that charges high rates. An eUICC or multi-IMSI approach  lets you switch to a favourable carrier deal. 

    How eSIMs compare to standard SIMs

    When it comes to IoT applications, there’s really no reason not to choose an MFF2 eSIM over the conventional form factors. But it’s still helpful to see them side-by-side and compare basic specs.

    Here’s a visual comparison of each SIM form factor:

    SIM FF

    And here are their dimensions:

    Form Factor Table

    As you can see, an eSIM is about one-tenth the size of a 2FF mini SIM, and it’s significantly smaller than even a 4FF nano SIM.

    For more information on these difference check our glossary page about the difference between an eSIM and a Nano SIM.

    eUICC vs. Multi-IMSI

    Another option to get better coverage and work with multiple operators is to use a SIM with a multi-IMSI applet. Each International Mobile Subscriber Identity (IMSI) is like a different MNO profile, and when you switch IMSIs, you don’t have to rely on your primary operator to develop a new integration and provision the SIMs. 

    Even when you change IMSIs and carriers, all your information stays in the same management portal. EMnify offers Multi-IMSI SIMs that automatically change IMSIs when they enter different regions or countries to select the best networks and carrier relations. 

    Considering an eSIM for your IoT application?

    At EMnify, we specialize in cellular M2M connectivity. Using Multi-IMSI technology, our eSIMs let your devices seamlessly select the best network wherever they’re deployed, and you can effortlessly manage your devices from a single, intuitive dashboard. If you have any questions about eSIMs or the best connectivity solution for your business, our team is always happy to help and offer advice.

    Download your eSIM now and get started.


    Jean-Eudes Ambroise

    Jean-Eudes is Director of Customer Success at EMnify. He's been working in the industry since 2017 and is an IoT expert.

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