Somewhere between buying a plan and boarding, there's a two-minute window where your iPhone quietly learns to live a double life: one line for home, one for wherever you're going. Apple buried the switch in a menu that sounds more like a phone company org chart than a feature, so here is the whole thing, step by step, with none of the guessing.
Before you start
You need three things, and you likely already have two if you're reading this on the phone in question: an iPhone from the last several years (eSIM has shipped since the XS), unlocked from your home carrier, and a Wi-Fi connection for about ninety seconds. If you're not certain about the unlocked part, our compatibility checker will tell you plainly rather than let you guess mid-install.
Installing the eSIM
Go to Settings > Mobile Service > Add eSIM. From here you have two routes in, and both end at the same place. If you were emailed a QR code, tap "Use QR Code" and point the camera at it - iOS reads it the way it reads a boarding pass, no app required. If your plan supports one-tap installation instead, a prompt appears directly on the phone once you're signed in on the account page; tap it, confirm, and the profile downloads without a camera at all.
Either way, give it a few seconds. "Downloading eSIM" is doing genuine work: fetching your profile and writing it to the phone's built-in chip. When it finishes, you'll have two lines listed under Mobile Service - your home one and the new travel one - for the first time.
Telling your iPhone which line does what
This is the step people skip, and the one that causes most of the confusion afterwards. Under Mobile Service, tap into the new line and check two settings:
- Default Voice Line - leave this on your home SIM. Calls and texts should keep routing the way they always have; a travel eSIM is a data line, not a replacement phone number.
- Mobile Data - switch this to your new travel eSIM, and turn on Allow Mobile Data Switching if you want iOS to fall back to your home line automatically once the travel data runs out.
Get this pairing right and the whole trip runs invisibly: calls behave as normal, data comes from the line built for the destination.