An eSIM is a SIM card built into your phone that you activate by scanning a QR code rather than inserting a plastic card. For travel it lets you buy a local data plan before you land and switch to it on arrival, while keeping your normal SIM active for calls and texts.

Does an eSIM replace my normal SIM?

No. Your normal SIM stays active for calls and texts while the eSIM handles data. Most travel eSIMs are data-only and have no phone number of their own, so SMS verification codes still arrive on your usual number.

Which phones support eSIM?

iPhone XS, XR and later, Google Pixel 3 and later, and most Samsung Galaxy phones from the S20 generation onward. Devices bought in mainland China generally lack eSIM, and carrier-locked phones must be unlocked first.

What is an eSIM?

A SIM card built into your phone that you activate by scanning a QR code, instead of a plastic card you push into a tray. For travel, it means you can buy a local data plan before you land and switch to it on arrival — without touching your normal number.

That last part is the bit that matters and the bit most explanations bury. Your normal SIM stays active for calls and texts. The eSIM handles data. You are not replacing anything.

How it works, in four steps

Buy a plan online for wherever you're going. You get a QR code, usually within a minute.
Scan it in your phone's settings, on wifi, before you leave. This installs the profile; it doesn't start the clock.
Land, and switch data over to the new eSIM. Most plans start counting from first connection, not from purchase.
Leave your normal SIM on for calls and texts, with its data turned off so it can't roam by accident.

Why bother

The comparison isn't eSIM versus a local SIM card, it's eSIM versus your own carrier's roaming rate. Roaming is typically charged per day whether you use it or not, and a travel eSIM is usually a fraction of that for a week or more abroad. You also skip hunting for a shop at the airport.

What the sellers don't lead with

Almost all travel eSIMs are data only. No phone number, so SMS verification codes won't arrive on them. Keep your normal SIM active for that.
"Unlimited" has a speed limit. Most unlimited plans slow down after a few gigabytes a day. Unlimited gigabytes, not unlimited speed.
Hotspot may be capped separately. Some unlimited plans allow only 1GB a day of tethering, worth checking if you plan to work off a laptop.
Validity is wall-clock. A 7-day plan expires on day 7 whether you used it or not.
Your phone must be carrier-unlocked. A locked phone will only accept profiles from the carrier it's locked to.

Does my phone support it?

Broadly: iPhone XS, XR and later (2018 onward), Google Pixel 3 and later, and most Samsung Galaxy from the S20 generation onward, including the Z Fold and Z Flip lines and many A-series models.

Two big exceptions worth knowing: devices bought in mainland China generally ship without eSIM, and carrier-locked handsets won't accept a third-party profile until they're unlocked. Full compatibility guide →

How much data will you actually need?

This is where most people get talked into buying too much. Normal phone use runs around 1GB a day; light use is closer to half that. The thing that really moves the number is tethering a laptop, which adds roughly 2.5GB a day on its own.