eSIM vs physical SIM: what’s the difference?

eSIM vs physical SIM at a glance.

A physical SIM is a small card you slide into your phone; an eSIM is a chip already built in, and you download your plan onto it. If the idea is new to you, start with what an eSIM is. Three terms worth knowing:

• SIM: your network’s chip card, which connects your phone to its network.
• eSIM: the same thing, but built into the phone. You install it with a QR code or an app.
• Dual SIM: two lines on the same phone, for example a SIM card and an eSIM.

Installing and switching plans.

Physical SIM: open the tray with the SIM tool, place the card and close it. Your phone detects it by itself.

eSIM: go to your phone’s settings, add an eSIM and scan your QR code. You need an internet connection, such as your Wi-Fi at home. With Mobile Companion, it takes 1 minute, from the app or with the QR code.

Switching plans follows the same logic. With a physical SIM, you need the new card in your hand. With an eSIM, you download the new plan and choose which line to use in your settings. The old one can stay on the phone, switched off, until you remove it.

Travelling abroad with each.

This is where the gap widens. With a local SIM card, you buy it when you arrive, take out your UK SIM and keep it safe until you get home. With a travel eSIM, you buy it online, install it at home and you’re online as soon as you land. Your UK SIM stays in place, so you keep your number.

• Before you leave: you buy and install the eSIM from home, on Wi-Fi.
• When you land: no queue at a counter and no tiny card to handle.
• During your stay: your UK SIM keeps your number for calls and texts, and the eSIM takes care of data.

For Japan, the Mobile Companion eSIM runs on NTT docomo’s network, in 5G where it’s available and 4G elsewhere, and it connects by itself when you arrive.

To weigh up the options once you’re there, read our guide to buying a SIM card in Japan.

Losing or changing your phone.

If your phone is lost or stolen

A SIM card can be taken out of a stolen phone and slipped into another. An eSIM can’t: a thief can’t take it away and use it elsewhere. To delete it, they’d have to go through the settings, which means unlocking the phone.

On Google Pixel, you can even ask for your screen lock before any eSIM is deleted: turn on Confirm SIM deletion in the security settings (Google help).

The flip side: if your phone is lost or broken, you can’t slide your line into another one. You’ll need a new eSIM, or a transfer where that’s possible.

If you’re changing phones

Here the physical SIM wins: you move it from one phone to the other in seconds. With an eSIM, you transfer it in your settings, when the provider supports it, or you get a new eSIM.

Buying a new phone? Check that it’s one of the eSIM-compatible models.

Can you use both at once?

Yes, on dual SIM phones, and many phones that support eSIM are dual SIM. You can keep your physical SIM for your number and add an eSIM for data, or run two eSIMs. How many lines can be active at the same time depends on the model: often two.

When you travel, this is the set-up to aim for. Your UK SIM stays switched on, so your number can still receive calls and texts, and the travel eSIM is your mobile data line. Turn off data roaming on your UK SIM so it doesn’t use data abroad. Depending on your UK plan, your network may charge for some services abroad, such as calls you receive: check before you go.

Which should you choose for Japan?

If your phone supports eSIM, an eSIM is the simpler route for a trip to Japan: you set it up at home and your UK SIM stays where it is. A physical SIM card still makes sense if your phone doesn’t support eSIM.

Off to Japan? Get a Japan eSIM for your trip, from €1.20 and ready before you fly.

FAQ.