What Is an eSIM and How Does It Work?

An eSIM (embedded SIM) is a SIM built into your phone that you set up by downloading a mobile plan instead of inserting a plastic card, so you can add or switch networks in a few minutes from your phone's settings.

Last checked: 15 October 2026

Some people search for it as "e sims", an "e-SIM" or a "virtual SIM card", but they all mean the same thing. This guide explains how an eSIM works, how it compares with a physical SIM and the newer iSIM, how eSIMs work with UK networks and how to use one when you travel.

What is an eSIM?

A traditional SIM card is a small removable chip that tells a mobile network who you are. An eSIM does the same job, but the chip is soldered inside the phone and cannot be removed. Instead of swapping cards, you download a "profile" from a network. The profile holds the details the network needs to recognise you, such as your account and security keys, and, for a phone plan, your number.

Because the chip is rewritable, one phone can store several eSIM profiles and switch between them. That is why eSIMs suit travel: keep your UK SIM for calls and texts and add a data eSIM for your destination.

The technology follows standards set by the GSMA, the global mobile industry body, so an eSIM from one provider works on any compatible, unlocked phone. You can read the GSMA's own overview on its eSIM page.

How does an eSIM work?

Setting up an eSIM is called "provisioning". In practice it takes a couple of minutes:

1. Buy a plan. You choose a plan from a network or an eSIM provider online or in an app.
2. Get the install details. You receive a QR code, an activation code or an install link.
3. Add it to your phone. On an iPhone, go to Settings, Mobile Service (or Mobile Data), then Add eSIM. On most Android phones it is under Settings, Network and Internet (or Connections), then SIMs or SIM manager, then Add eSIM.
4. The profile downloads. Your phone connects securely to the provider's server and installs the profile. You need Wi-Fi or mobile data for this step.
5. Choose which line to use. You can label each line (for example "UK" and "Travel") and pick which one is used for mobile data.

The download is encrypted and authenticated under the GSMA standard, so a profile can only be installed on the phone it was issued for. Treat your QR code like a password and never share it. Our guide to eSIM scams and fake QR codes explains why.

Most phones can store several eSIMs, but usually only two lines can be active at the same time, for example a physical SIM plus one eSIM, or two eSIMs. Apple says iPhones can store eight or more eSIMs. For step-by-step screenshots, see how to set up an eSIM on different devices.

eSIM vs physical SIM vs iSIM

There are now three forms of SIM. They all do the same job of identifying you to a network. The difference is where the SIM lives and how you change it.

For a phone user, an iSIM behaves just like an eSIM. It saves a little more space and power for device makers, which matters most for small devices such as trackers and smart watches.

Is a "virtual SIM card" the same as an eSIM?

Usually, yes. When people search for a virtual SIM card they normally mean an eSIM: a SIM you download rather than insert. Be careful, though, because "virtual number" apps are something different. Those apps give you an extra phone number that works over the internet. They do not connect your phone to a mobile network, so they cannot give you mobile data on their own.

A travel data eSIM is the opposite: it gives you mobile data on local networks abroad but usually comes without a phone number. You can still use WhatsApp, FaceTime and other apps over data, and keep your UK number on your main SIM. See how to keep WhatsApp and your UK number with a travel eSIM.

eSIMs in the UK

All the big UK networks support eSIM for pay monthly plans, including EE, O2, Vodafone and Three, along with many smaller networks such as giffgaff, Sky Mobile, Tesco Mobile, iD Mobile, SMARTY and VOXI. Support for pay as you go varies, so check with your network. A UK survey by FDM CCS Insight, published in January 2026, found close to three in four UK mobile users had heard of eSIM and almost a quarter had used a travel eSIM (source).

• Moving your UK number to an eSIM: you request an eSIM from your own network, usually in its app, online account or in store. Your number stays the same.
• Your phone must be unlocked to use another provider. Since December 2021, Ofcom rules have stopped UK networks selling locked phones, but older handsets can still be locked. Check before you travel. On an iPhone, go to Settings, General, About and look for "No SIM restrictions" next to Carrier Lock.
• Dual SIM is standard. Most phones sold in the UK take a physical SIM and an eSIM, so you can keep your UK SIM in place and add a travel eSIM alongside it.
• Some phones are now eSIM-only. The iPhone Air has no SIM tray anywhere, and Apple says the new iPhone Duo is eSIM-only worldwide. UK versions of the iPhone 17 range, the Pixel 10 and 11 and the Galaxy S26 still have a SIM tray, but US versions of many of these phones are eSIM-only. Apple lists which models take which SIM on its SIM support page.

The main reason UK travellers use eSIMs is cost. Since Brexit, most UK networks charge a daily fee to use your allowance in Europe and much more further afield. Our guide to UK roaming charges in 2026 sets out what to expect.

Using an eSIM when you travel

A travel eSIM is a data plan for the country or region you are visiting. You buy it before you go, install it at home on Wi-Fi and switch it on when you land. Your UK SIM stays in the phone for texts such as bank codes.

• Install before you fly. You need an internet connection to download the profile. See when to install a travel eSIM.
• Turn off data roaming on your UK line so you are not charged by your home network. Our dual SIM settings guide walks through it.
• Pick the right size. Light users often manage on 1GB to 3GB a week. The travel data calculator can help.
• Know the limits. Most travel eSIMs are data-only. They do not include a local number, and they do not change the law in the country you visit.

SimplySIM sells data-only travel eSIMs for more than 190 countries, paid in pounds. Check your phone first with our device compatibility checker, then browse plans from the homepage.

Pros and cons of eSIMs

Advantages

• Add a plan in minutes, with no shop visit or post.
• Keep your UK number active while using a cheaper data plan abroad.
• Nothing to lose or damage, and no SIM tool needed.
• Store several plans and switch between them.
• Less plastic and packaging than physical SIM cards.

Disadvantages

• Not every phone supports eSIM, and some cheaper or older models do not.
• A locked phone may refuse another provider's eSIM.
• You need an internet connection to install the profile.
• If you delete an eSIM by mistake, you may need your provider to reissue it.

How to check if your phone supports eSIM

The quickest test is to dial *#06#. If the screen shows an EID number, your phone has eSIM hardware. You can also look in your phone's mobile or SIM settings for an "Add eSIM" option.

Most iPhones from the XR and XS onwards, Google Pixel phones from the Pixel 3 onwards and Samsung Galaxy S20 and later flagships support eSIM, but some regional versions do not. Our full guide, Is my phone compatible with eSIM?, lists current models, or use the compatibility checker to look up your exact phone.

FAQs

What does eSIM stand for?

eSIM stands for embedded SIM. It is a SIM chip built into your device that stores mobile plans you download, rather than a card you insert.

Is an eSIM better than a physical SIM?

For most people it is more convenient, especially for travel, because you can add a plan in minutes and keep your UK SIM at the same time. Network coverage and speed are the same, as both connect to the same mobile networks.

Can I have an eSIM and a physical SIM at the same time?

Yes, on dual SIM phones. Most recent iPhones, Pixels and Samsung Galaxy phones sold in the UK let you use a physical SIM and an eSIM together.

Do eSIMs work in the UK?

Yes. EE, O2, Vodafone, Three and many smaller UK networks offer eSIMs for UK plans, and travel eSIM providers such as SimplySIM sell eSIMs for use abroad.

Does a travel eSIM give me a phone number?

Most travel eSIMs, including SimplySIM plans, are data-only. You keep your UK number on your main SIM and use apps such as WhatsApp for calls and messages over data.

What is the difference between an eSIM and an iSIM?

Both are downloadable SIMs. An eSIM is a separate chip inside the device, while an iSIM is built into the device's main processor. For users they work the same way.