eSIM explained - getting clear on the term's many meanings

June 22, 2021

In the telco world we use abbreviations for everything, right? Sometimes the meaning of these abbreviations becomes tangled up with each other, and the same term can suddenly mean two different things. The use of the term “eSIM” is often either misinterpreted or has different meanings, depending on who you’re talking to. So let’s clear up the term eSIM!


Let’s sort this out, so you will know what to ask for when searching for global IoT eSIM connectivity or when you are looking to buy eSIM cards. Here are the key distinctions that are worth knowing.

Definition 1

The physical form factor of the SIM card

When the term “eSIM’’ is used to describe the physical form/shape of the SIM card, it is usually referred to as an “Embedded SIM card”. This can be compared to a regular plugin SIM in different sizes. The most common form of this eSIM is usually referring to the MFF2 form factor - in this case it is the “small black square” designed to be placed directly on the motherboard/module, without the use of a SIM card holder. 

The MFF2 is the most common standardized Embedded SIM used. However, there are others in the industry as well, including BGA (Ball Grid Array), DNFQ8 and WLSCP (Wafer Level Chip Scale Packaging) just to be able to fit into the smallest sizes.

Definition 2

A SIM card with the technical characteristics of reprogrammable mobile operator profiles

The technical term for a SIM card with the ability to reprogram an Operator Profile on the SIM card is “eUICC”. The eUICC can be any SIM card form factor, as pictured above. The capability to download and activate different Operator Profiles on a single physical SIM card of any form factor allows for many benefits, including switching SIM profiles over the air from one carrier to another, flexibility in global deployments of connected devices as well as when it comes to scalability.

Key takeaways

  • There is only one type category of eSIM’s if referring to the physical shape and form factor of a SIM card.
  • All physical SIM form factors can be eSIM’s if referring to the eUICC feature.
  • An Embedded eUICC is referring to the MFF2 form factor which can be reprogrammed with different Operator Profiles.
  • So be aware of the use of the term eSIM and use it with confidence knowing what the different definitions are!


​​​​​I hope this gives you more clarity on the topic.

If you are interested to learn more about whether eSIM could help with connecting devices you are working with, or want to find out about the UROS Connect service built on eUICC technology, feel free to reach out.

Oscar Falkman, ​​​​Chief Strategy Officer

Oscar Falkman

Chief Strategy Officer

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