What is an eSIM? A simple explanation.

eSIM meaning in plain English.

eSIM stands for “embedded SIM”. It’s a small chip built into your phone that does the same job as a SIM card: it connects your phone to a mobile network. The difference? There’s no card to slide in. Your plan is downloaded straight onto the chip.

People often say “eSIM card”, even though there’s no card to handle. Four terms worth knowing:

• eSIM: the chip built into your phone. It can hold several plans.
• eSIM profile: the technical name for the plan you download onto that chip. Think of it as your SIM card, in digital form.
• QR code: the square code you scan to install your plan. It tells your phone where to download it from.
• EID: the identity number of the eSIM chip. If your phone shows one in its settings, it supports eSIM.

How does an eSIM work?

You buy an eSIM online, from a mobile network or from a travel eSIM provider. You then get what you need to install it: a QR code to scan, or a guided set-up in an app. Your phone downloads the profile over Wi-Fi or another connection and adds it as a new line. From then on, it connects to the network like any SIM.

Once it’s installed, you can switch the line on or off in your settings, and choose which line handles calls and which handles mobile data. For the whole journey, from buying to getting online, here’s how a travel eSIM works, step by step.

eSIM vs physical SIM card.

A physical SIM card slides into a tray on the side of your phone; an eSIM is already inside, and you download your plan instead. Installing, travel, security and changing phones are compared side by side in eSIM vs physical SIM: the differences.

Pros and cons of an eSIM.

Which phones support eSIM?

Most recent smartphones support eSIM, but not all of them. To check yours:

• On iPhone: go to Settings > General > About and look for the “EID” line.
• On Android: type “*#06#” on the phone app’s keypad. If an EID number appears, your phone supports eSIM. If not, search for “eSIM” in your settings.
• In every case, your phone must be unlocked: a phone locked to one network can refuse other providers’ eSIMs.

The list by brand is here: phones that support eSIM. And if you buy in the Mobile Companion app, it checks your phone before you buy.

Is an eSIM secure?

Yes. An eSIM uses the mobile network like any SIM, and it can’t be pulled out of a lost or stolen phone. To remove it, someone has to unlock your phone first, so your usual screen lock is what protects it. What happens if you lose or change your phone is covered in eSIM vs physical SIM.

When you travel, a data eSIM also means you rely less on public Wi-Fi in stations, cafés and hotels: you stay on a mobile network, just as you do at home.

Why travellers use an eSIM.

Travel is where an eSIM really shows its worth. Your phone keeps your UK SIM and adds a local eSIM, just for data. In practice:

• you buy and install it before you leave, from home;
• you’re online as soon as you land, with no shop or Wi-Fi to hunt for;
• your UK SIM stays in place, so your number stays with you;
• you use a local network instead of roaming on your UK plan.

For Japan, Mobile Companion offers a data eSIM on NTT docomo’s network, in 5G where it’s available, with a real Japanese IP address. It installs in 1 minute and connects by itself when you arrive. You can even share your connection with your laptop or a friend’s phone. Getting one takes three steps:

1. 1

   Choose your plan

   On the website or in the Mobile Companion app, from €1.20 for 1 GB to €28.90 for 50 GB. The app checks that your phone is compatible before you buy, and your QR code arrives straight away.

2. 2

   Install it at home

   From the app or by scanning your QR code, on Wi-Fi: it takes 1 minute.

3. 3

   Land and you’re online

   Turn off aeroplane mode and your eSIM connects to the Japanese network by itself. Your plan starts at your first connection in Japan, not when you buy it.

What about your phone number?

An eSIM can carry a phone number, just like a SIM card: that’s the case with eSIMs from mobile networks. Travel eSIMs are often data-only. Mobile Companion is one of them: your eSIM doesn’t come with a phone number.

You don’t lose anything, though. Your UK SIM stays in place with your number, so you can still receive calls and texts on it, depending on your UK plan. WhatsApp and FaceTime keep working with your usual account, over the eSIM’s data.

Off soon? Get an eSIM for your trip to Japan, from €1.20, and install it before you go.

FAQ.