An eSIM, or embedded-SIM, is a SIM card permanently integrated into a device like a smartphone, tablet, or wearable, which cannot be removed. It is essentially a virtual SIM card profile installed on an eUICC (embedded Universal Integrated Circuit Card) chip, permanently attached to the device during manufacturing. This eUICC chip has the same electrical interface as a physical SIM but is smaller in size, measuring 6 mm × 5 mm.

How eSIM functions:

1. Activation: With eSIM, you can activate a cellular plan from your carrier without the need for a physical SIM card. This typically involves turning on your new device and following on-screen instructions.
2. Multiple profiles: An eSIM-compatible device can store multiple "eSIM profiles," each akin to a physical SIM card, complete with its own phone number and data plan. For example, an iPhone can support multiple eSIMs, allowing you to use multiple phone numbers concurrently.
3. Remote provisioning: eSIMs are typically provisioned remotely, enabling users to add or remove operators without physically swapping a SIM card. This convenient feature simplifies carrier switching and accessing local cellular services when traveling abroad.
4. Permanent eSIM ID: All eSIMs come with a permanent eSIM ID (EID) programmed at the factory. This EID is used by the provisioning service to link the device to an existing carrier subscription and to establish a secure channel for programming.
5. Compatibility: eSIM adheres to the global specification defined by the GSMA (Global System for Mobile Communications Association) and is supported by major operating systems such as iOS, Android, and Windows. This technology is now supported by various devices, including smartphones, tablets, and wearables.

In summary, eSIMs offer a seamless and flexible way to manage your mobile connections without the need for physical SIM cards. They are a global standard supported by various devices and operating systems, making them a convenient choice for many users.

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