What Is an eSIM? How It Works, Setup Tips and Travel Benefits
- Nico Dudli
- Jun 14
- 9 min read
Updated: 6 days ago
Quick Answer
An eSIM is a digital SIM built into your phone, tablet, smartwatch or laptop. Instead of inserting a plastic SIM card, you install a mobile profile digitally through an app, QR code or your device settings.
For travellers, the biggest advantage is simple: you can keep your home number active for calls, texts, WhatsApp and two-factor codes while using a separate travel eSIM for mobile data abroad.
In practice, an eSIM does not improve signal strength by itself. It gives your device access to a mobile network. Speed, coverage and reliability still depend on the local network, your location and your device.
What Is an eSIM?
An eSIM, short for embedded SIM, is based on a chip permanently built into your device. Technically, this chip is called an eUICC, or Embedded Universal Integrated Circuit Card.
Instead of inserting a removable SIM card, you download a mobile profile onto this built-in chip. That profile tells your device which mobile network it can connect to and which data plan it should use.
Depending on the provider, setup works through:
a provider app
a QR code
an activation code
your phone’s mobile settings
Once installed, the eSIM appears in your device settings like a regular SIM line. You can usually label it, turn it on or off, select it for mobile data and switch between profiles.
How Does an eSIM Work?
The technical foundation for consumer eSIMs comes from the GSMA, the international mobile industry association. The key process is called Remote SIM Provisioning.
In simple terms:
You buy an eSIM plan from a provider.
The provider creates a secure digital mobile profile.
Your device downloads that profile through the internet.
The profile is stored on the built-in eSIM chip.
Your phone uses that profile to connect to a mobile network.
This is why you need Wi-Fi or an existing internet connection to install most eSIMs. Once the profile is downloaded and activated, the eSIM can connect to the mobile network at your destination.
eSIM vs Physical SIM
A physical SIM is a removable plastic card. An eSIM is a digital profile stored on a built-in chip.
Physical SIM:
You insert a card into your phone.
Switching plans often means swapping cards.
The card can be lost or damaged.
It may be easier to move between devices.
eSIM:
You install the profile digitally.
You can store multiple profiles on many devices.
There is no plastic card to lose.
It is especially useful for travel, dual SIM setups and temporary data plans.
For most travellers, the eSIM is more convenient. You can buy and install a plan before departure instead of looking for a local SIM shop after landing.
Why eSIMs Are Useful for Travel
The main travel benefit is dual SIM usage.
On a compatible phone, you can keep your regular SIM active and use a travel eSIM only for mobile data.
This means:
your home number stays reachable
WhatsApp keeps working with your existing number
banking codes and two-factor authentication still arrive
mobile data runs through the travel eSIM
you avoid depending fully on expensive roaming
This is the setup I use on my own trips: home SIM for identity, calls and messages; travel eSIM for data.
One important warning: calls and SMS on your home SIM may still cost money abroad, even if mobile data uses the eSIM. Always check your carrier’s roaming terms before you travel.
How to Set Up an eSIM
The setup process is similar across most travel eSIM providers:
Choose your destination and data plan.
Buy the eSIM before your trip.
Install it through the provider app, QR code or activation code.
Label the profile clearly, for example “Travel eSIM”.
Keep your main SIM active for calls and SMS.
Set the travel eSIM as your mobile data line.
Enable data roaming for the travel eSIM at your destination.
Keep data roaming disabled on your home SIM unless you intentionally need it.
My most important tip: set up the eSIM at home over Wi-Fi before you leave. Take a screenshot of the setup details, save your order number and check which SIM is selected for mobile data.
Most eSIM problems are not caused by the eSIM itself. They are usually settings issues: the wrong data line is selected, roaming is disabled, the eSIM is not activated, or the APN is missing.
For detailed setup instructions, use these guides:
Which Devices Support eSIM?
Not every phone supports eSIM, so always check compatibility before buying a plan.
iPhone:Apple has supported eSIM since the iPhone XS, iPhone XS Max and iPhone XR. Newer iPhones can usually store multiple eSIM profiles. iPhones sold in mainland China typically do not support eSIM.
Android: Many newer Samsung Galaxy S and Z models, Google Pixel phones and selected other Android devices support eSIM. Compatibility can vary by region, carrier and model.
A quick check on many phones: dial *#06#. If your device shows an EID, it usually has an eSIM chip.
Tablets, watches and laptops: Some iPad Cellular models, Apple Watch models and Windows laptops also support eSIM.
Before buying a travel eSIM, check three things:
your device supports eSIM
your device is unlocked
your destination is covered by the provider’s plan
Does an eSIM Improve Signal or Speed?
No. An eSIM does not magically improve reception.
The SIM format only controls access to a mobile network.
Signal and speed depend on:
the local carrier network
your exact location
indoor or outdoor conditions
network congestion
your device’s antenna and supported bands
whether you are on 4G/LTE or 5G
This is important because some people expect an eSIM to fix bad coverage. It cannot. If the local network is weak in a mountain valley, on a train or inside a stadium, an eSIM cannot create coverage where the network has none.
What it can do is give you a practical way to access another network or avoid expensive roaming.
Real-World Experience: What I Actually Tested
I have used travel eSIMs regularly for several years across Europe, Asia and North America. My tests are based on real travel use, not lab simulations.
Teaching an Online Class on Mobile Data
One of my most demanding eSIM tests was in Port de Sóller, Mallorca. I taught a live online class with around 25 participants using video, audio and screen sharing.
The connection stayed stable for the full session. That mattered more than a speedtest number, because a dropout would have been immediately visible to everyone in the room.
Hotspot for Multiple Devices
In Montpellier, I used a Saily eSIM as a hotspot for two MacBooks and two smartphones at the same time.
In the city centre, I measured up to 354 Mbps download. At a café, I measured 70.94 Mbps, which was still enough for video calls, browsing and agency work across multiple devices.
Full report: Saily eSIM France Review
Road Trip Navigation
In Austria and Portugal, I mainly used travel eSIMs for navigation, messaging and travel planning. The connection was reliable on the routes I drove.
In remote areas and mountain valleys, coverage can still drop. That is usually a local infrastructure issue, not an eSIM-specific problem.
More on European coverage: Saily eSIM Europe Review
Trains and Network Reality
Germany gave me the clearest reminder of what an eSIM cannot solve. In Munich city centre, I measured strong 5G performance. On an ICE train between Hannover and Hamburg, performance dropped significantly during the journey.
The takeaway: an eSIM simplifies access to mobile data. It does not remove the real-world limits of local network infrastructure.
For my broader hands-on testing notes, read: Saily eSIM Review: My Real Travel Experience
Travel eSIM Providers I Use
For travel, I mainly compare Saily, Holafly and Airalo.
Saily
Saily is my main travel eSIM choice for many trips because the app is simple, the plans are easy to understand and regional options are useful for multi-country travel.
I have tested Saily in more than twelve countries, including Switzerland, France, Germany, Italy, Spain, Portugal, Thailand, Vietnam, Singapore and the UAE.
Useful Saily guides:
For the latest tested Saily discounts and coupon conditions, use my dedicated coupon page instead of relying on outdated codes in old articles: Saily Coupon Codes 2026
Holafly
Holafly is my second option, especially when I want unlimited data and do not want to calculate exact GB usage in advance.
Unlimited plans can be useful for heavy users, but they are not always the cheapest choice. The better option depends on your destination, trip length and expected data use.
Comparison: Holafly vs Saily
Airalo
Airalo is one of the best-known travel eSIM providers and is often worth comparing, especially for simple destination-based data plans.
My direct comparison: Saily vs Airalo
Best eSIM Guides by Destination
If you already know where you are travelling, these guides are more useful than a general eSIM explanation:
Pros of an eSIM
Fast setup: You can buy and install the plan before departure.
No physical card: There is nothing to lose, damage or swap.
Home number stays active: You can keep calls, texts, WhatsApp and two-factor codes on your normal number.
Multiple profiles: Many devices can store several eSIM profiles.
Good for multi-country trips: Regional plans can cover several countries with one profile.
Useful as a hotspot: Many travel eSIMs allow hotspot use, depending on provider and plan.
Predictable cost: You know the price, data amount and validity before you travel.
Cons of an eSIM
Not every device supports it:Older devices and some regional models do not support eSIM.
Device switching can be harder:Many travel eSIMs cannot simply be transferred to another phone.
Most travel eSIMs are data-only:You usually do not get a local phone number for calls or SMS.
You need internet to install it:Use Wi-Fi or an existing connection before departure.
Settings matter:Wrong data line, disabled roaming or missing APN settings can block the connection.
Network quality is not guaranteed:An eSIM uses local partner networks. Performance depends on local infrastructure.
Common eSIM Problems and Quick Fixes
If your eSIM does not work after landing, check these points first:
Is the eSIM profile installed?
Is the eSIM turned on?
Is it selected as the mobile data line?
Is data roaming enabled for the travel eSIM?
Is data roaming disabled on your home SIM?
Is the APN correct?
Have you toggled flight mode on and off?
Have you restarted the device?
Are you in an area with actual network coverage?
For the full troubleshooting guide, read: Saily eSIM Problems 2026
Frequently Asked Questions
Do I need internet to install an eSIM?
Yes. You usually need Wi-Fi or an existing mobile connection to download the eSIM profile. Install it at home before you travel whenever possible.
Can I keep my normal phone number?
Yes. On a dual SIM phone, you can keep your home SIM active for calls, texts and WhatsApp while using the eSIM for mobile data.
Do I need to enable data roaming?
For most travel eSIMs, yes. The eSIM connects to a local partner network, so data roaming must usually be enabled for the travel eSIM. Make sure you do not accidentally enable roaming on your home SIM if you want to avoid roaming charges.
Can I use WhatsApp with an eSIM?
Yes. WhatsApp usually continues working with your existing number, even if mobile data runs through the travel eSIM.
Can I use an eSIM as a hotspot?
Usually yes, but it depends on the provider and plan. I have used Saily as a hotspot for multiple devices during real travel tests.
Can I transfer an eSIM to a new phone?
For regular carrier plans, this may be possible. For travel eSIMs, transferring or reinstalling the same profile on another device is often restricted. Do not delete the eSIM profile before checking your provider’s terms.
Is an eSIM more secure than a physical SIM?
An eSIM cannot be removed from your phone and inserted into another device. That can be an advantage if your phone is stolen. However, an eSIM does not protect you from phishing, weak passwords, compromised accounts or an unsecured phone.
Does an eSIM improve signal strength?
No. The SIM format does not improve reception. Signal quality depends on the local network, your location and your device.
What if I have signal bars but no internet?
Check whether the travel eSIM is selected for mobile data, whether data roaming is enabled and whether the APN is correct. A flight mode toggle or restart often helps.
Is an eSIM better than roaming?
Often, yes — especially for international travel where your home carrier charges high roaming fees. But it depends on your carrier plan, destination and data needs.
Conclusion
An eSIM is one of the most practical travel upgrades you can use today. It replaces the plastic SIM card with a digital profile, lets you keep your home number active and gives you a simple way to use mobile data abroad.
The most important thing to understand: an eSIM is not magic. It does not fix weak local networks, train coverage gaps or overloaded stadiums. It gives your device access to a mobile plan. The actual performance still depends on the network behind it.
For my own trips, the value is clear. I can set up data before departure, keep my main number active and avoid relying on airport SIM shops or unpredictable roaming costs.
Start here if you want to compare real options:
About the Author
Nico Dudli is a digital entrepreneur, lecturer in Marketing and Digital Technologies, and the founder of TechNovice. He has tested travel eSIMs across more than 12 countries, including Switzerland, France, Germany, Italy, Spain, Portugal, Thailand and Vietnam. His eSIM reviews are based on real travel use, including live online teaching, hotspot work sessions, road trips and destination-specific network tests.
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