(
Embedded
Subscriber
Identity
Module) A storage chip in a phone that contains the name of the carrier, telephone numbers and data about the service. The eSIM is the built-in version of the removable card (see
SIM card).
With the traditional SIM card, changing numbers or carriers requires replacing the card in the device's SIM tray. In contrast, an embedded SIM is built in and programmed remotely by the carrier, which is especially helpful for people who travel frequently in different countries and must switch carriers.
Google's Pixel 2 phones and the Apple Watch 3 with Cellular were some of the first devices to employ eSIMs. iPhones (starting with the 11) can store eight phone numbers in their eSIMs, two of which can be made active. eSIMs are also used in wireless machine-to-machine devices that have permanent identities. See
SIM card.