How the eSIM works – and what it’s good for


Sooner or later, the SIM cards to be inserted into the device will be shut down. Over the decades they have shrunk from credit card size to mini and micro format and today, as nano SIMs, are no bigger than the little fingernail. Soon they could be gone completely.

This is made possible by the eSIM, which has been around for seven years. It replaces the physical SIM card with one that is firmly soldered into the device. The eSIM contains the same data as a conventional SIM card. These can be downloaded via an Internet connection, saved on the module and then used just like in a conventional SIM card.

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By 2025, around a third of the smartphones in use around the world should connect via eSIM, predicts the GSMA, the global industry association of mobile network operators. Actually, that would be a fine thing for customers and providers. Providers save themselves the time-consuming mailing process, and customers can use a new SIM card directly when ordering online. But somehow the change to the new technology may not really get going.

Only upper-class smartphones have an eSIM built-in – at Google, for example, the Pixel 3, and at Apple, all current models. At Samsung you can only find the eSIM in the top devices, currently for example in the Galaxy Note20 and the current Galaxy S21 5G. At Huawei it is the P40 and P40 pro models. The latest flagships from OnePlus, on the other hand, do not have an eSIM on board. Oppo and Xiaomi do not offer any models with eSIM.

eSIMs can also be found in some tablets, especially in current iPad models and high-quality business notebooks. The manufacturers are happy to install them in wearables such as the Apple Watch or the Samsung Galaxy Gear S2. In principle, the eSIM could be used in any device that is equipped with cellular access.

The eSIM has a major advantage for device manufacturers: You no longer have to plan a SIM drawer. If all the openings to the outside for the charging sockets, headphone connection and also the SIM drawer are omitted, a smartphone can be constructed much easier and cheaper, completely dustproof and waterproof. Motorola has already taken this step with the Razr 2019 and has omitted the conventional SIM. However, the device was only sold in small numbers in Germany.

When it comes to wearables, size is another important factor: the eSIM is a tiny chip that can be packaged in a suitable place on a circuit board. A SIM drawer, on the other hand, requires a comparatively large volume and can only be placed on very specific surfaces or edges of the housing, making the device more voluminous and mechanically more sensitive and restricting the freedom of the designer.

Such drawers are also prone to mechanical defects. Customers who insert cards incorrectly or force manually inaccurately cut cards into the device can seriously damage it. And even if the customer does everything right: despite the gold coating, sliding contacts always remain a possible source of error.

There is also potential in the card for cell phone providers and consumers. With an eSIM, new customers can access the network within minutes of signing an online contract. If a device is lost, the replacement device can be used immediately after uploading the eSIM data without having to order a physical replacement card. The expensive logistics for SIM cards from production to shipping are no longer necessary. Instead, SIM card profiles can be created as required and transferred to the eSIM in the customer’s device within a few seconds.

What is a convenience gain with normal mobile phone contracts and devices is a must for IoT devices. In systems that are built into the depths of industrial plants, household appliances or motor vehicles, you can’t just change the SIM card. The eSIM allows this not only contactless, but ultimately even fully automatically if required in cooperation with the provider. The use of eSIMs is already widespread in IoT applications and the market is growing rapidly because more and more devices use an Internet connection.