What is an eSIM and how does it work?
An eSIM is a digital SIM integrated into a compatible device that allows you to use a mobile service without inserting a physical SIM card. Instead of changing small plastic chips, the profile needed to connect to a network is installed digitally on the phone. It is the evolution of the traditional SIM card and follows international standards developed by the GSMA, the global organisation of mobile operators.
This technology is especially useful when travelling: you can arrange a connection for your destination before leaving, keep your usual SIM and use a second line for mobile data. This way, you avoid having to look for a local SIM card as soon as you land and can prepare much of your connection in advance.
An eSIM, e-SIM or virtual SIM allows you to digitally install a mobile service on compatible phones. It can coexist with a physical SIM, makes it easier to switch between lines and is especially practical abroad. With eSimFLAG, you can buy a plan for your destination, install the eSIM before travelling and automatically connect to the corresponding network when you arrive.
What is an eSIM and what is it used for?
eSIM stands for embedded SIM, meaning integrated SIM. Although terms such as virtual SIM, digital SIM, eSIM card, e sim or e-sim are also used, the fundamental difference compared with a traditional SIM is that you do not need to insert a physical card to install a new mobile profile.
It is used to activate mobile services on compatible devices and manage different lines with greater flexibility. You can use it as your usual line or purchase a travel eSIM to have Internet in another country.
How does an eSIM card work?
An eSIM card works by downloading a digital configuration onto your phone so that it can connect to the network without using a physical chip. It is a 100% secure process regulated by the GSMA.
For the user, the process is much simpler: purchase the service, install the eSIM and configure which line you want to use for mobile data. Depending on the provider and device, installation can be done using a QR code, transfer, the operator's app or manual configuration.
How to activate an eSIM
The exact activation process depends on the provider. With eSimFLAG, the process can be summarised in four steps:
- Check that your phone is eSIM-compatible and unlocked.
- Buy the plan for your destination and the days of your trip.
- Install the eSIM before travelling, preferably with a stable Internet connection.
- During the flight or when you arrive, select eSimFLAG as your data line, activate its roaming and deactivate roaming on your usual line.
Once configured, the eSIM automatically connects to the corresponding local network when you arrive at the destination you purchased the plan for.
How to switch between a physical SIM card and an eSIM
If your phone supports Dual SIM, you can have your usual SIM card and an eSIM on the same device and choose which one to use for calls, messages or data, depending on the capabilities of each line.
On iPhone, for example, you can select in the settings which line is used for mobile data. Compatible Pixel devices also allow you to choose which SIM you want to use for different functions. The specific menu names may vary depending on the manufacturer and operating system.
eSIM vs physical SIM: advantages, disadvantages and differences
An eSIM and a physical SIM both identify a line on a mobile network, but the way they are managed differs considerably.
| Feature | eSIM | Physical SIM |
|---|---|---|
| Format | Digital and integrated into the device | Removable physical card |
| Installation | Digital profile | Inserted into the SIM tray |
| Switching lines | From the phone settings | May require changing the card |
| Buying for travel | Can be done online | You need to have the physical card |
| Dual SIM | Available on compatible devices | Depends on the device |
| Risk of losing it | There is no physical card to keep | Can be lost when removed |
| Compatibility | Only devices prepared for eSIM | Broad compatibility |
Among the main advantages of eSIM are convenience, digital purchase and the possibility of keeping another line on compatible phones. The only requirement? Having a compatible phone. In return, you also gain security: if your phone is stolen, nobody can remove the SIM card to use your line.
When is it worth using an eSIM?
An eSIM is especially useful when you want to add a second line without handling your usual SIM, separate different mobile services or stay connected during an international trip.
It is also practical if you visit several destinations and want to organise your connection before leaving. With eSimFLAG, the eSIM remains installed on the device and allows you to subsequently add new plans, so it can be reused on future trips.
How do I know if my phone is compatible with eSIM?
Before buying an eSIM card for travelling, always check the exact model of your device. It is not enough to know that you have an iPhone, Samsung, Google Pixel or Xiaomi, because there may be differences depending on the model and the market in which it was sold.
iPhones compatible with eSIM
Apple has supported eSIM since the iPhone XS, XS Max and XR and later models, although there are exceptions depending on the country or sales region. Some current models are even sold without a physical SIM tray in certain markets.
Therefore, before buying an eSIM for iPhone, it is advisable to check the specific model in the eSimFLAG checker.
Android devices compatible with eSIM
On Android, compatibility depends on the manufacturer and model. Families that include eSIM devices include Google Pixel, Samsung Galaxy and other manufacturers, but not every device from the same brand includes this feature.
Google, for example, offers Dual SIM compatibility on numerous Pixel devices and allows you to manage eSIM profiles from the device settings.
Why use an eSIM for travelling?
A travel eSIM allows you to arrive in another country with your connection ready, without looking for a local shop or removing your usual card. You can continue using apps such as WhatsApp, Google Maps, transport services, email or social networks from the moment you have a mobile connection.
In addition, on compatible phones you can keep your personal line and use the eSIM for travel data. Apple expressly supports using one personal line and one travel line through Dual SIM.
Why choose eSimFLAG's eSIM?
Because you can completely forget about counting gigabytes. eSimFLAG is designed to keep you connected from the moment you land, with unlimited data in more than 170 destinations, the freedom to share your Internet connection with your companions and Telefónica's technical support (eSimFLAG by Movistar).
It is also extremely practical: the same eSIM does not expire and remains on your phone, so you can reuse it by adding new days or countries on your next trips without installing anything else. And if you have any questions during your journey, you have a support team available 24 hours a day directly via WhatsApp.
Keep in mind that these plans are focused exclusively on Internet connectivity (they do not include traditional calls or SMS), but you can continue using WhatsApp, app-based calls or maps without any problem.
How to use an eSIM during a trip
Imagine that you are going to spend a week in another country. The process with eSimFLAG can be prepared almost entirely before you leave:
Step 1. Check compatibility
Search for your phone model in the eSimFLAG checker and confirm that the device is unlocked.
Step 2. Select the destination and days
Choose where you are travelling and how long you need the plan for.
Step 3. Install the eSIM
Follow the instructions received by email. eSimFLAG recommends installing it before travelling and with a stable Internet connection.
Step 4. Configure mobile data
Select eSimFLAG as the data line, activate its roaming and deactivate roaming on your usual line.
Step 5. Connect when you arrive
When you reach the destination you purchased the plan for, the plan starts being used when the device connects to the corresponding network.
Frequently asked questions about eSIMs
Does an eSIM replace a physical SIM?
It can replace it, but you do not necessarily have to choose one or the other. Many phones allow you to use a physical SIM and an eSIM together, while certain models sold in some countries work exclusively with eSIM.
Can I have a physical SIM card and an eSIM at the same time?
Yes, as long as the device is compatible with Dual SIM. For example, certain iPhones and Google Pixel devices allow you to combine a physical SIM and an eSIM.
Does an eSIM change my phone number?
No, not simply because it is an eSIM. The number depends on the line you purchase. With a travel data eSIM such as eSimFLAG, you can keep your usual SIM and main number while using the eSIM to connect to the Internet.
Do I need an eSIM to travel?
It is not essential. You can use your operator's roaming, Wi-Fi or buy a local SIM. However, a travel eSIM is convenient because you can purchase and install it before arriving and do not need to physically change cards.
How many eSIMs can I have installed?
It depends on the device. There is no universal number. Apple states that compatible iPhones can store eight or more eSIMs, although the number that can remain active simultaneously is lower. Other manufacturers set their own limits.
Does an eSIM work without coverage?
No. Just like a physical SIM, an eSIM needs a compatible mobile network to be available in order to provide a connection. If there is no coverage in a particular location, the eSIM cannot create it by itself.
Is an eSIM secure?
Yes. An eSIM uses specific technical standards for the provisioning and management of mobile profiles. In addition, because it is integrated into the device, it cannot be physically removed like a traditional SIM if the phone is lost or stolen.
How much does an eSIM cost?
It depends on the operator, destination, duration and type of service. With an international travel eSIM, the price usually depends on the country or region and the number of days purchased. eSimFLAG displays updated prices for each destination before purchase.
What happens if I change phones?
It depends on the company. Some allow you to transfer the profile from one phone to another easily, while others require you to generate a new QR code. With eSimFLAG, ideally, you should not delete it from your phone so that you can continue adding plans to it in the future.
Can I make calls with an eSIM?
Yes, an eSIM can provide voice, SMS and data if the purchased plan includes these services. eSimFLAG, specifically, is a data eSIM and does not allow conventional voice traffic or SMS. You can make calls over the Internet using apps such as WhatsApp while you have a data connection.
Do I need Internet to activate an eSIM?
You normally need an Internet connection to download and install the eSIM profile. eSimFLAG recommends installing it before travelling. Afterwards, certain phone settings, such as selecting the line or activating roaming, can be configured without a connection.
Can I use an eSIM abroad?
Yes. In fact, international eSIMs are specifically designed to make it easier to stay connected while travelling. With eSimFLAG, you can select a compatible destination, install the eSIM before leaving and use the purchased plan when you connect in that country or region.
Which operators offer eSIM in Spain?
There are currently numerous operators offering eSIM in Spain. These include Movistar, O2, Orange, Vodafone, DIGI, Yoigo, Pepephone and Jazztel, although conditions, compatibility, prices and activation processes vary between companies.
For travelling abroad, in addition to the eSIM you may be able to use with your usual operator, you can purchase a travel eSIM such as eSimFLAG, designed to provide mobile data in the included destinations without having to replace your usual card.