What is an eSIM? How the digital SIM card works

A conventional SIM card is a small computer chip (technically a UICC, «Universal Integrated Circuit Card») on which your operator stores your subscriber identity and the keys your device uses to authenticate itself on the network. With an eSIM, this chip is soldered onto the circuit board and is called an eUICC, «embedded UICC». The GSMA defines it in its architecture specification SGP.21 as «a UICC which enables the local management of Profiles in a secure way». So the difference lies not in the chip itself but in the fact that it ships empty, and everything the plastic card used to bring with it can be loaded on afterwards.

The GSMA calls this loading Remote SIM Provisioning (RSP). The operator has a profile generated on a server, the SM-DP+: a package of data and applications that is encrypted and tied to the unique identifier of your chip, the EID («eUICC Identifier»). Your device runs a small piece of software called the Local Profile Assistant (LPA); on iPhone and Android it is part of the operating system and appears to you as the «Add eSIM» menu. The LPA opens a secure connection to the server, checks that the profile fits your chip, downloads it and installs it. You then switch it on, and from that moment the profile behaves on the network exactly like an inserted SIM card.

For the LPA to know where to collect the profile, it needs an activation code. The GSMA describes it as information the operator issues to the end user so that they can request the download and installation of a profile. In practice you usually meet this code as a QR code you scan with the camera, more rarely as a string of characters to type in. Some operators manage without any code at all: with so-called carrier activation, the operator registers the profile for your EID and your device finds it by itself through a discovery service. Apple calls this «eSIM Carrier Activation» in its support pages, Samsung «eSIM Simple Setup».

The rules for all this are laid down in public specifications of the GSMA, the worldwide association of mobile operators. SGP.21 describes the architecture for consumer devices (currently version 3.1 from May 2026), SGP.22 the technical implementation; alongside them, SGP.31 and SGP.32 form a separate variant for devices without a screen such as sensors or meters (GSMA, as at 21 October 2026). Because every manufacturer and operator implements the same specifications, an eSIM from a Swiss operator such as Swisscom works on an iPhone exactly as it does on a Galaxy, and a travel eSIM from Singapore installs on a Pixel bought in Europe.

The most obvious advantage is time: an eSIM is ready to use as soon as you order it, whereas a physical card comes by post. Swiss operator Swisscom, for instance, says its eSIMs are usable immediately while a plastic card takes two days to arrive, and for security reasons it does not post cards abroad at all. If you lose your phone abroad, an eSIM is therefore the only quick way to get your number back. Then there is the price: at Swisscom and Sunrise the eSIM profile is free, while a physical replacement card costs CHF 40 and CHF 59.90 respectively (as at 21 October 2026).

The second advantage is space. A device with a single SIM tray can still run two numbers with an eSIM, for example a private and a work number, or your main number and a travel eSIM. According to Apple, an iPhone stores eight or more eSIMs and from the iPhone 13 can use two at the same time; Google likewise quotes two simultaneously active eSIM profiles for the Pixel 7 and later. Mobile data, however, only ever runs over one line: according to Apple, the iPhone can use only one mobile network for data at a time.

The third advantage is security if the device is lost. Apple describes the eSIM as more secure than a physical SIM because it cannot be removed if the iPhone is lost or stolen. A thief cannot simply pop the card into another phone to use your number or intercept SMS codes. Google describes embedded eSIMs as «more secure and less damage-prone» than physical cards: a chip that is never taken out cannot get scratched or lost either.

There are drawbacks all the same. A physical card moves into a loan device, an ancient handset or a mobile router in ten seconds; with an eSIM you need either the manufacturer's transfer feature or a new profile from your operator. Setup almost always requires an internet connection, usually Wi-Fi. Older or very cheap devices have no eUICC at all. And not every feature works with every combination: in Switzerland, for instance, Samsung's own support page lists only Swisscom as supporting the convenient «eSIM Instant Transfer», not Sunrise or Salt (as at 10 September 2026). For most people the advantages outweigh the drawbacks, but if you swap devices often, check beforehand how your operator handles transfers.

Apple: according to Apple Support, every iPhone from the iPhone XS, iPhone XS Max and iPhone XR onwards supports eSIM, as does the third-generation iPhone SE. Among iPads, only «Wi-Fi + Cellular» models qualify, such as the iPad Pro from the third generation (12.9-inch) or first generation (11-inch), the iPad Air from the third generation, the iPad from the seventh generation and the iPad mini from the fifth generation. Smartwatches with mobile connectivity such as the Apple Watch or the Galaxy Watch also run on an eSIM; operators usually add them to your plan through a multi-device option (Swisscom in Switzerland calls it «Multi Device», for instance).

Google: the Pixel help pages list eSIM support for Pixel phones; running two eSIM profiles at once requires a Pixel 7 or newer according to Google. Airalo's compatibility list includes Pixel models from the Pixel 2 to the Pixel 11, with exceptions for certain Pixel 3 variants from Australia, Taiwan and Japan or on particular US plans (as at September 2026).

Samsung: Samsung's support page names as eSIM-capable the Galaxy S range from the S20 to the S26 (including Plus, Ultra and Edge variants), the Galaxy Z range (Fold, Flip), the FE models from the S23 FE to the S26 FE and many Galaxy A models, where support depends on the region. Among tablets, the Galaxy Tab S9 to S11 and the Tab Active5 are included, but only in their mobile-network versions: «Wi-Fi only tablet models do not support eSIM functionality.» With Samsung in general, the device should have been produced for Europe; Airalo, for example, excludes Galaxy devices from China, Hong Kong and Taiwan as well as the US models of the S20, S21 and Note 20 Ultra.

Other manufacturers and laptops: Airalo's list additionally covers models from Motorola, OnePlus, Xiaomi, Sony, Honor, Huawei, Nokia, Oppo and others, often only for certain regions, because the same model name is sold with or without an eUICC depending on the market. Add to that Windows laptops with an LTE modem from Acer, Asus, Dell, HP, Lenovo and Microsoft Surface. Airalo itself stresses that the list is not complete; if in doubt, check the manufacturer's technical specifications.

How to check your own device: dial *#06# in the Phone app. If a 32-digit EID number appears next to the IMEI, your device has an eUICC and supports eSIM. This test comes from Airalo's help centre and works the same way on iPhone and Android. Important for travel eSIMs: the device must not be network-locked. On an iPhone you can see this under «Settings» > «General» > «About»; according to Apple, «No SIM Restrictions» must appear next to «Service Provider Lock». How the setup then works in detail is shown in our step-by-step guide (→ How to set up an eSIM: step-by-step guide for iPhone & Android).

Since the iPhone 14 range, Apple has sold iPhones without a SIM tray in the US. According to Apple's overview «Learn which type SIM your iPhone or iPad uses», the iPhone 14, 15 and 16 (each including the Plus, Pro and Pro Max models) are eSIM-only if bought in the US; the same models from other countries have a nano-SIM tray plus eSIM. With the iPhone 17 range, Apple widened the circle: according to Apple, the iPhone 17, iPhone 17e and the iPhone 18 Pro and 18 Pro Max have no SIM tray if bought in the US, the US Virgin Islands, Canada, Mexico, Japan, Guam, the United Arab Emirates, Saudi Arabia, Bahrain, Kuwait, Qatar or Oman. Apple lists the iPhone Air as a pure eSIM device without any country restriction (as at 21 October 2026).

In Europe, then, iPhones are still sold with a SIM tray, with the exception of the iPhone Air. With iPads, Apple has gone a step further: according to Apple, the iPad Pro with M4 and M5 chips, the iPad Air with M2, M3 and M4, the iPad (A16) and the iPad mini (A17 Pro) are available in their mobile-network versions with eSIM only, regardless of the country of purchase.

Google is heading the same way: according to the Pixel help pages, the Pixel 10, Pixel 10 Pro and Pixel 10 Pro XL support eSIM only in the US. Nothing changes for buyers in Europe for now, but the direction is clear: the eSIM is going from optional extra to standard. If you want to use a US-bought iPhone in Europe, you need an operator that issues eSIM profiles (the three Swiss operators Swisscom, Sunrise and Salt all do, for instance), and according to Apple you should check beforehand that the device's mobile bands match the network.

Mainland China is a special case: there, according to Apple, only the iPhone 18 Pro, iPhone 18 Pro Max, iPhone 17e and iPhone Air support eSIM at all; older Chinese models have two nano-SIM trays instead. This matters for travel eSIMs because Airalo excludes most iPhones from China, Hong Kong and Macau from its compatibility list.

Operators that offer eSIM usually do so for both contract and prepaid plans, but they differ in how you order one and what it costs. The common route is the customer portal or app: you request an eSIM for your existing number, and the operator either shows you a QR code to scan or, with carrier activation, pushes the profile straight to your device without any code. New customers pick the eSIM option when signing up online or in a shop. Some operators hand out a printed voucher with a QR code instead. Whichever way it works, the setup needs an internet connection, ideally Wi-Fi, and automatic activation may only work in the operator's home country: Swisscom, for instance, says it is not possible abroad and offers a call-back instead.

Many operators treat the eSIM profile as the cheaper or free option, because there is no card to produce and post. The three Swiss operators illustrate the range we found when we read their help pages on 21 October 2026: Swisscom issues eSIM profiles free of charge in «My Swisscom» while a physical SIM carries an activation fee of CHF 40, and its app installs the profile on an iPhone directly without a QR code; Sunrise likewise charges nothing for a new eSIM profile in «My Sunrise» but CHF 59.90 for a new plastic card; Salt works with a QR-code voucher that you receive by post or in a Salt Store, where the eSIM costs CHF 59. Your number stays the same when you move from a nano-SIM to an eSIM. Prices change, so the operator's own page is what counts.

One thing to understand before you switch: a profile is tied to one device. As Sunrise puts it, a QR code is linked to a single device; when you change phones, a new profile is created and the old one is deactivated once the new one is active. The same profile can usually be downloaded again on the same device free of charge, but on a new device you need either the manufacturer's transfer feature or a fresh profile from your operator, and some operators ask for a valid ID document in your customer account before they transfer a number. Operators such as Swisscom let you keep several eSIM profiles with different numbers on one device.

A few practical details apply almost everywhere. If you move from a physical SIM to an eSIM, take the old, deactivated card out of the device afterwards; Salt points out that the phone otherwise keeps trying to connect with it. Check the SIM PIN: on Salt's eSIM, for instance, it is switched off by default, the PIN is printed on the voucher and you can enable it in the device settings. And before you sell or pass on a device, reset it to factory settings: according to Swisscom and Salt, that deletes the eSIM profile from the device. Services tied to your SIM, such as Mobile ID in Switzerland, continue to work with an eSIM according to Salt.

Smartwatches and tablets use the same number as your phone through a multi-device option. At Swisscom, «Multi Device» runs the plan on up to five additional devices for CHF 10 per device per month, with up to four devices included on blue Mobile L and up to five on blue Mobile XL and inOne mobile premium; the eSIM for the extra device is ordered in «My Swisscom» under «Devices & SIM» and set up with a QR code. If you live in Switzerland, our guide explains which roaming rules apply to your main number in the EU (→ EU roaming from Switzerland 2026: how to avoid the cost trap).

For travellers the eSIM is the real breakthrough. Instead of buying a local prepaid card at the airport or paying your home operator's expensive roaming rates, you load a data eSIM from a provider such as Airalo, Holafly, Saily or Nomad onto your phone before you leave. Apple's travel guide describes two kinds: local providers in your destination country, which often include a local phone number and sometimes ask for ID, and worldwide providers with prepaid data plans for over 190 countries. Which of them suit you is covered in our comparison (→ Best travel eSIM 2026: Airalo, Holafly & Saily compared); we put the two biggest names head to head in (→ Airalo vs Holafly 2026: the honest comparison).

The principle is dual SIM: your main number stays active and reachable on the first line, and the travel eSIM takes over data on the second. Apple's travel guide describes exactly these two options, using the travel eSIM on its own or alongside your home line. Because most travel eSIMs are data-only, you keep using your home SIM for calls and texts, for example for bank codes. According to Apple, only one number can use mobile data at a time; on an iPhone you set the travel eSIM as the data line under «Settings» > «Mobile Service» > «Mobile Data».

The most important step is to switch off data roaming on your home line, or at least make sure it is not selected as the data line. Apple warns in its travel guide that roaming fees from your home plan may still apply when you use both lines. From iOS 26, according to Apple, the iPhone asks on arrival whether you want to use only the travel eSIM or both lines, and depending on the country it automatically turns the travel eSIM off when you return; after that, check that your primary line is active for data again. For Pixel phones, Google recommends activating a prepaid travel eSIM only after you arrive at your destination, so that the validity period does not start at home.

Check three things before you book: the device must support eSIM, it must not be network-locked according to Airalo, and it must not be jailbroken or rooted. Best practice is to install the profile at home on Wi-Fi but activate it only at your destination. We have dedicated guides for the most popular destinations: Turkey (→ Best eSIM for Turkey 2026: prices, networks & our pick), the USA (→ Best eSIM for the USA 2026: prices & providers compared) and Japan (→ Best eSIM for Japan 2026: 5 providers compared); for trips around Europe, (→ Holafly Europe eSIM 2026: is unlimited worth it?) has the details on an unlimited data package.

When you change phones you cannot simply move an eSIM across; it has to be transferred to the new device. There are two ways: the manufacturer's transfer feature, which works without contacting your operator, or a new profile from your operator that you install on the new device with a QR code or app. Once activated on the new device, the old profile becomes invalid; a number cannot be active on two devices at the same time.

iPhone to iPhone: Apple calls the feature «eSIM Quick Transfer». According to Apple, both devices must be signed in with the same Apple Account and unlocked, Bluetooth must be on, and both need iOS 18.4 or later; from iOS 26 you can transfer several phone numbers at once. On the new iPhone, go to «Settings» > «Mobile Service», tap «Add eSIM» and choose «Transfer From Nearby iPhone», confirm on the old device and enter a verification code if prompted. A physical SIM can also be converted into an eSIM on the new iPhone this way. From iOS 26, according to Apple, some operators also support switching between Android and iPhone; otherwise you contact your operator.

Android to Android: on Pixel phones you transfer the SIM during setup or later under «Settings» > «Network & internet» > «SIMs» > «Add SIM» > «Transfer SIM from another device». According to Google, both devices need Android 12 or later, the current Google Play services and a screen lock; the process can differ slightly depending on the operator, and if the transfer is not detected, the operator has to activate the eSIM. Samsung calls its version «eSIM Instant Transfer»: on the new Galaxy you choose «Transfer SIM from Galaxy/Android phone» and enter a six-digit code on the old device; for moving from an iPhone to a Galaxy there is «Transfer SIM from iPhone» via QR code. Operator support varies: in Switzerland, for instance, Samsung lists only Swisscom as supporting it (as at 10 September 2026). Operators may add their own requirements, too: Sunrise requires at least Android 14 with One UI 6 on the new device and Android 13 with One UI 5 on the old one.

If the transfer fails or your operator does not support it, order a new profile in the customer portal: free of charge at Swisscom and Sunrise, via a new voucher at Salt. After installing, Swisscom and Sunrise recommend restarting the device. A tip from Swisscom's help pages: if the setup fails, delete the faulty profile from the device first and only then set up the new one.

At the technical level, the eSIM is no less secure than the card: according to the GSMA, it offers an equivalent level of security and protection to the removable SIM card. The profile is transmitted encrypted and tied to the EID of your chip, so an intercepted QR code cannot be redeemed at will on another device once the profile has been installed. If the device is lost or stolen, the eSIM is actually at an advantage, because nobody can take the card out and put it in another phone. Even so, you should have the number blocked straight away in your operator's customer portal or app, where SIM and eSIM profile can be blocked in the same way.

The real weak spot is not the chip but your customer account with the operator. The Swiss National Cyber Security Centre (NCSC) describes two cases from Switzerland in its weekly reviews. In 2023, a victim clicked a phishing link sent in the name of their mobile operator and entered their login details; the attackers logged in to the customer portal, ordered a new SIM and thereby gained access to every account linked to that number, including codes sent by SMS. The victim was cut off from the network during this time. In 2024, the NCSC described a case in which the attackers additionally tricked the victim into handing over an SMS code through a fake prize draw, used it to create an eSIM and then, one after the other, took over the victim's email account, Apple account, cloud backup and crypto apps via the number; according to the NCSC the loss came to over CHF 20,000. This method is called SIM swapping, and it works just as well with a physical SIM as with an eSIM, the difference being that an eSIM reaches the attacker faster because nothing has to be posted.

What the NCSC concludes from this applies to every mobile contract: switch on two-factor authentication wherever you can; never enter passwords or credit card details on pages you opened via a link in an email or text message; use passwords of at least twelve characters and a different one for each service; and never pass SMS codes on to anyone, not even to supposed employees of your operator. According to the NCSC, warning signs are a phone that suddenly has no reception even though the network is there, or logins that stop working; if that happens, call your operator immediately.

In terms of privacy, the eSIM changes little: your operator knows, as before, who you are and where your device logs on to the network. With travel eSIMs, a further provider comes into play that carries your data and, depending on the country, asks for ID details. With the travel eSIM's IP address you appear online as a user in that country or in the provider's country; what that means is explained in our guide to IP addresses (→ How to find your IP address – and what it reveals about you) and our article on when a VPN makes sense (→ Do you really need a VPN in 2026? The honest guide).

«An eSIM is a different network or a different plan.» No. The eSIM is just a different way of getting your operator's profile onto the device. Coverage, speed, plan and phone number stay exactly the same; according to Apple, roaming with an eSIM works just as it does with a physical SIM.

«With an eSIM I'm tied to my phone.» Only to a degree. The profile really is tied to the eUICC of one particular device, but Apple, Google and Samsung offer transfer features, and operators issue a new profile when needed. Switching takes a little longer than moving a card, but it is no obstacle.

«I can only have one eSIM.» Quite the opposite: according to Apple an iPhone stores eight or more eSIMs, Google speaks of multiple profiles on the Pixel, and operators such as Swisscom allow several profiles with different numbers on one device. Depending on the device, two lines are active at the same time, and mobile data only ever runs over one of them.

«A travel eSIM replaces my main number.» Usually not. Most travel eSIMs supply data only and no phone number; calls and texts continue to run over your home line as long as you leave it switched on. That is precisely why dual SIM is the norm when travelling. Which providers we recommend for this is in our comparison (→ Best travel eSIM 2026: Airalo, Holafly & Saily compared); we took a close look at one of the best-known providers in a separate assessment (→ Holafly review 2026: prices, limits & honest verdict).

«An eSIM can be hacked remotely.» According to the GSMA architecture, downloading a profile requires the user to confirm the process on the device, and the transfer is encrypted end to end between server and chip. The cases documented by the Swiss NCSC did not go through the technology but through stolen login details for the customer portal: phishing, in other words, not the eSIM itself.