An eSIM is a SIM card that is already inside your phone. Instead of a piece of plastic you slot in, the eSIM is a chip soldered to the board, and a network writes its details to it over the internet. The practical result is that changing network, or adding a second number, becomes a five minute job you can do from your sofa.
Written September 2026. Exact menu names vary by phone and by network, but the process below is the same everywhere.
Why an eSIM is worth caring about
Three things change once your phone supports eSIM, and the third is the one that saves real money.
- Switching networks takes minutes. No waiting for post, no hunting for the pin that opens the tray. You scan a QR code or tap through an app and the line is live.
- You can hold two numbers at once. Most phones with an eSIM support at least one eSIM plus a physical SIM, and many support two eSIM profiles. A work number and a personal number on one handset, or your home number kept active while you use a local plan abroad.
- Travel data stops being extortionate. This is the big one. Instead of paying your home network’s roaming rate, you buy a local or regional eSIM data plan before you fly, install it, and land with working data at local prices.
How to set up an eSIM
You need a phone that supports it, which means most flagships from 2018 onward and nearly everything current, and a network that offers it. The steps:
- Check compatibility. On iPhone, Settings, General, About, and look for an EID number. On Android, Settings, About phone, and look for the same. If there is an EID, the phone has an eSIM.
- Buy the plan. Your existing network can usually convert a physical SIM to an eSIM free. For travel, buy from a travel data provider before you leave.
- Install the profile. You will get a QR code or an activation code. On iPhone, Settings, Mobile Service, Add eSIM. On Android, Settings, Network and internet, SIMs, then add.
- Label the line. Give it a name such as Travel or Work. This matters more than it sounds once you have two lines and need to pick which sends a text.
- Set your defaults. Choose which line is used for calls, for texts and for mobile data. On a trip, the sensible setting is local eSIM for data and home line for calls, with roaming off on the home line.
The transfer trap when you change phone
Here is the thing that catches people out, and it is worth knowing before you stand in a shop with two phones. A physical SIM moves by hand. An eSIM does not exist as an object, so it has to be transferred, and how easily depends on your network.
Recent iPhones and Android devices offer a direct eSIM transfer during setup, moving the profile from the old phone to the new one over Bluetooth. When it works it takes a minute. When the network does not support it you have to request a new activation code, which can mean a call to support and, occasionally, a wait.
Two rules avoid the pain. Do not factory reset or trade in the old phone until the new one has a working line, because wiping the old device can destroy the profile. And if you are travelling, do the transfer before you go, not in an airport with poor wifi.
Before you hand the old phone on, work through our checklist on what to do before you sell your phone, which covers the backup and sign-out steps that need to happen in order.
When a physical SIM is still better
An eSIM is not automatically the right choice. A physical SIM is easier to move to a spare handset if your phone dies, easier to hand to a family member, and works on cheap secondary devices that may not support eSIM at all. If you travel to places where you buy a local SIM at a kiosk, plastic is often still faster and cheaper than a travel eSIM plan.
The sensible arrangement on a dual-capable phone is one of each: your main number on the eSIM, where switching is easy, and the tray free for a local SIM when it makes sense. If you are planning a trip, our travel tech checklist covers what to sort out before you fly.
Choosing a travel data plan
The market for travel data is crowded and the pricing is deliberately hard to compare. A few rules cut through it.
- Match the plan to the trip, not the country. Regional plans covering a continent are usually better value than separate country plans if you are crossing borders, and worse value if you are not.
- Check whether you get a phone number. Most travel data plans are data only. That is fine for messaging apps and maps, but it means no ordinary calls or texts, which matters if a bank wants to send you a code.
- Look at what happens when the data runs out. Some plans stop, some throttle, some charge. The last is the one to avoid.
- Watch the validity window. Plans usually start counting from first connection, not from purchase, but not always. Read that line before you buy.
- Install before you fly. You generally need internet to install the profile, which is exactly what you will not have at the airport.
For a two week holiday, a regional data plan plus your home number left on for texts only is usually the cheapest arrangement that still lets your bank reach you. Turn data roaming off on the home line so it cannot quietly bill you.
When it does not connect
Most problems come down to three things. Check that the new line is enabled at all, under your mobile or SIM settings. Check that mobile data is pointed at the right line, because adding a line does not switch data over automatically. And check that data roaming is on for the travel line, which sounds wrong but is often required because the plan technically roams onto a local partner network.
If the profile will not install, the usual cause is a QR code that has already been used. An activation code works once. If you deleted the profile, you generally need a fresh code rather than the original one.
Common questions
Can I use an eSIM and a physical SIM at the same time? Yes on most modern phones. That is the usual arrangement for keeping a home number active while using a local data plan abroad. Some newer phones drop the tray entirely and support two eSIM profiles instead.
Does an eSIM work when I change phones? It has to be transferred rather than moved by hand. Recent phones offer a direct transfer during setup; otherwise your network issues a new activation code. Do not wipe the old phone until the new line is working.
Is an eSIM cheaper for travel? Usually, and often dramatically. Buying a local or regional data plan as an eSIM avoids your home network roaming rate. Compare it against your operator’s travel add-on, which is occasionally competitive for short trips.
Does an eSIM use more battery? No meaningfully. Running two active lines at once uses slightly more power because the phone maintains two connections, but the eSIM itself is not the cause.
Sources and further reading
Where the figures and rules above come from, so you can check them:
- Device compatibility and the EID check: GSMA
- Apple’s eSIM setup and transfer documentation: Apple Support
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