What is an eSIM and how does it work?

If you have never used one, an eSIM sounds like something for engineers. It is not. It is the same SIM card you have always had, just without the piece of plastic: instead of pushing it into a tray, you download it by scanning a QR code. Five minutes, wifi, done.

This guide covers exactly that: what it is, how it differs from a physical SIM, which phones take one, how to install it step by step, and what to look at when it will not connect. No jargon.

What an eSIM actually is

Inside your phone there is a tiny chip soldered to the board. That chip is the eSIM (embedded SIM). It sits empty until you load a profile onto it: the data that tells it which operator the line belongs to, what plan it has and how to authenticate on the network.

That profile is what you buy when you buy “an eSIM”. It arrives as a QR code (or as a link, depending on the phone), you scan it, the phone downloads the profile, and from then on it behaves exactly as if you had slotted a card in.

One phone can hold several profiles at once, though usually only one or two are active. That is why you can keep your normal home line and add a travel data eSIM, then choose which one carries data and which one takes calls.

eSIM vs physical SIM

	Physical SIM	eSIM
How it arrives	By post, in a shop or at the airport	By email, in seconds
Installing it	Pop the tray with the pin, swap the card	Scan a QR on wifi
Your usual number	Left in a drawer at home (or swapped every time)	Stays in the phone, active
Losing it	It is a bit of plastic: it gets lost and it snaps	Cannot be lost
Changing country	Another card, another queue	Another QR, or a regional plan
Requirements	Any phone with a tray	Compatible, unlocked phone

The real catch is that last row: not every phone takes an eSIM, and the ones that do have to be carrier-unlocked. Everything else is in its favour.

Which phones take an eSIM

The list grows every year, but broadly:

• iPhone: from the iPhone XR and XS (2018) onwards, including every SE from the second generation on. Models sold in the United States from the iPhone 14 are eSIM-only.
• Google Pixel: from the Pixel 3 (with the odd exception depending on where it was bought).
• Samsung Galaxy: the S series from the S20, the Z series (Fold and Flip), the Note 20 and several recent A models.
• Others: many mid-range and high-end Xiaomi, Motorola, Oppo, Sony, Huawei and Honor phones from the last two or three years.

The quick way to settle it is to dial *#06# on the phone: if an EID appears among the numbers (a 32-digit string), the phone has an eSIM. If you only see the IMEI, it does not. The full list by brand and model is on the compatibility page.

Two warnings worth knowing:

1. Unlocked phone. If you bought it on a contract and it is still locked to the carrier, a travel eSIM will not work. Ask your operator to unlock it — in Spain they are obliged to do it free once the contract ends. Ask early.
2. Imported or Chinese models. The same model can have an eSIM in its European version and not in its Asian one. If the phone came from abroad, the *#06# test is what counts.

How to install it, step by step

Do it at home, on wifi, without rushing. Installing the eSIM does not start it: the plan begins the first time the phone connects to a network at your destination, so you can have it ready days or weeks in advance.

On iPhone

1. Open the email with the QR code on another device (a laptop, a tablet, someone else’s phone) so you can scan it with the camera. If you only have the one iPhone, most providers also include a link or a code you can paste by hand.
2. Settings → Mobile Data → Add eSIM → “Use QR Code” → scan.
3. Give it a name you will recognise: “Trip”, “Japan”, whatever. It saves confusion later in settings.
4. When it asks about your default line and your mobile data line, leave your usual line as the default (so you still get calls and texts) and pick the eSIM for data only. You can change this at any time.
5. Open the eSIM you just created and turn on Data Roaming. Without this it will show a network at your destination but will not browse: this is the number one mistake.

On Android

Menus vary a little by brand, but the path is always similar:

1. Settings → Connections (or Network & internet) → SIM manager / SIM cards → “Add eSIM” or “Download SIM”.
2. Scan the QR or paste the activation code by hand.
3. Set the eSIM as the mobile data line and leave your usual SIM for calls.
4. Inside the eSIM, turn on data roaming. On Samsung it is usually under SIM manager → tap the eSIM → Data roaming.

When you land

1. Turn off airplane mode (or switch the phone on).
2. Check that the eSIM is the data line and that your home line has data switched off. That is what avoids the bill shock: if your home tariff connects outside the EU, it charges by the megabyte or by daily bundles.
3. Within a few seconds the local operator’s name will appear. If it does not, toggle airplane mode on and off once — that usually does it.

When it starts and when it ends

Validity starts with the first real connection at your destination, not with the purchase and not with the installation. A 7-day plan you install on Monday in Madrid and first use on Saturday in Bangkok expires the following Saturday.

Plans count in one of two ways:

• By day with unlimited data: each day includes an allowance at full speed and, once you pass it, you stay connected at reduced speed until the next day. No cut-off, no extra charges.
• By GB with a fixed duration: a set amount of data (3 GB, 5 GB, 10 GB…) to spend over however long the plan lasts. When it runs out you top up or buy another.

Which one suits you depends on how you use your phone. The Spanish guide ¿Cuántos GB necesito para viajar? has a table with what each app really uses.

If it will not connect: what to check, in order

The vast majority of “it does not work” cases come down to one of these five:

1. Data roaming is off on the eSIM. This one wins by a mile.
2. Mobile data assigned to the wrong line. Check which line is set for data.
3. You are in the wrong place. A Japan eSIM will not find a signal on your stopover in Doha. Wait until you arrive.
4. Airplane mode. Toggle it off and on; sometimes the phone clings to a network the eSIM cannot use, and this makes it search again.
5. Manual network selection. If the plan works with several operators and the phone latches onto a bad one, go to the eSIM’s settings → Network selection → pick another by hand.

If none of that works, a full restart fixes more than you would think. And if it is still dead, write to support with your phone model and a screenshot of the eSIM settings — someone will look at it straight away.

Upsides and limits, without the sales pitch

The good part: you do not depend on the hostel wifi, you do not queue at the airport, you do not change your number, and you know what you are paying before you leave. On a multi-country trip, a regional plan saves you buying a card at every border.

What to be clear about: it is data only (no traditional calls), not every phone will take one, and the coverage is the local operator’s, not the eSIM’s — in a village with no mast, no eSIM on earth will help, ours included. If you are heading somewhere with genuinely poor rural coverage, read that country’s guide first.

MovaSim sells this kind of eSIM for 190+ destinations, with the QR by email in seconds. But the installation steps and the advice in this guide work just as well with any provider.