What is an eSIM?

Embedded SIM. It is a small chip permanently built into the phone that can be reprogrammed over the air, so a mobile plan is downloaded onto it rather than posted to you on a piece of plastic.

On the network side it is identical — same towers, same speeds, same coverage. The differences are practical: an eSIM can be bought and installed in two minutes from anywhere, cannot be lost or damaged, and lets a phone hold several plans at once. The trade-off is that it is harder to move between phones.

Yes, and this is the one that catches people out. Installing a profile is a download, so you need Wi-Fi or an existing data connection at the moment you install it — which is exactly what you will not have standing in an arrivals hall. Always install before you fly.

It is at least as safe as a physical SIM and arguably safer: nobody can pull it out of a stolen phone and use your number, and a profile is cryptographically tied to the device it was downloaded to.

Yes. Recent iPhones store eight or more profiles and can run two lines at once; most Android phones store several and keep one eSIM active. This is why a travel eSIM sits alongside your normal SIM instead of replacing it.

SM-DP+ is the server address your phone contacts to fetch the profile, and the activation code identifies which profile is yours. A QR code is just those two strings packaged so a camera can read them — which is why every order also shows them as text you can type in manually.