Definition
eSIM (embedded SIM) is a SIM integrated as a chip soldered directly into a device: carrier information is delivered as a profile that is downloaded and activated remotely, with no physical card to insert. Its behavior is defined by GSMA remote SIM provisioning specifications.
How it works
The device ships with an embedded eUICC chip; after the user picks a plan — often by scanning a QR code — the carrier’s encrypted profile is securely downloaded and activated on the chip. One eSIM can hold multiple profiles, so switching carriers no longer means swapping cards.
Usage
Dual-SIM phones, smartwatches with independent cellular, laptops with mobile broadband, and large IoT deployments all use eSIM to drop the physical card tray. Buying a local data plan online while traveling is an increasingly common use.
Related and confusable terms
eSIM is not a network generation or a radio technology — it is the user identity module. 5G and Wi-Fi describe how a device reaches a network; eSIM describes how a device proves to a cellular network who it is.