eSIM (Embedded SIM) — Definition

An eSIM, or embedded SIM, is a SIM built into your phone that activates over the air, with no physical card to insert.

Instead of slotting in a plastic chip, you scan a QR code or tap through a carrier app and the SIM profile downloads straight onto the phone. Recent iPhones sold in the US have gone eSIM-only, dropping the physical tray entirely.

In practice

An eSIM almost always sets up its own data settings when it activates, so you rarely touch the APN on an eSIM line. eSIMs also make travel easier, since you can buy and install a local or regional plan before you even land. Our guide on APN vs eSIM covers how the two relate.