How does an eSIM work? A simple guide for travelers and expats

You’re off on holiday in a few hours – exciting times! Passport – check. Suncream – check. Holiday spirit – check. Cheap overseas mobile plan…whoops! 

Fear not, this is where an eSIM plan could come to your rescue. eSIMs are tiny chips that are embedded into compatible phones and tablets and allow connection to a mobile network without a physical SIM card. Never used one? Our experts will walk you through how eSIMs work, how to set one up, which devices they’re compatible with, and the pros and cons. 

What is an eSIM?

eSIM stands for “embedded SIM”. It’s like a digital version of the SIM cards you’re probably already familiar with, and installs directly onto your phone – so, no need for a physical card. This means that, as long as you have a compatible device, you can have your main, physical SIM and multiple eSIMs installed on your phone at the same time. 

You can purchase an eSIM for most countries or regions, check the provider in advance to make sure they’re available in the area you need coverage for. When you sign up to an eSIM contract, your identity information is stored digitally on the eSIM. If a device has eSIM capability built in, it can store multiple eSIM profiles at the same time. The number of eSIMs you can store depends on the model. Modern iPhones can store 8+, while newer Android devices can typically store between 5 and 7. 

Storing isn’t the same as using, though; most devices only let you have 1or 2 active eSIMs at a time (in addition to your main, physical SIM). 

How does an eSIM actually work?

This is where it gets a bit technical, but we’ll do our best to explain it in plain English for those who like to get into the nuts and bolts of how things work. 

The eSIM chip is a rewritable piece of hardware – an embedded Universal Integrated Circuit Card (eUICC) permanently soldered into the phone.

To use an eSIM, instead of inserting a physical chip like you do when you change providers, you download a small software “profile” from an eSIM provider onto the eSIM. This profile holds all the information needed to identify you to the network provider. It does functionally the same job a physical SIM does, just delivered digitally.

The way eSIMs work has several advantages:

• You can switch networks on the same device.
• Some (though not all) eSIMs come with a dedicated phone number, allowing you to run two phone numbers from the same phone –if you wanted to use one for work and one for personal use, for example.
• You can set up a travel plan without ever touching your device’s hardware, saving you the faff of switching SIMs (and temporarily losing access to your main phone number) if you want to avoid high roaming charges abroad. 

Multiple profiles can be stored on the same eSIM chip; the phone’s software lets you switch which one is active. This can be a big help if you’re someone who splits their time between different countries. 

eSIM vs physical SIM: what’s the difference?

While both types of SIM perform an identical key function – connecting to a mobile network – there are a few key differences between physical SIMs and eSIMs. 

How to activate an eSIM: step-by-step

The process for activating an eSIM can vary slightly between providers, but typically follows these steps. Ideally installation should be done while connected to wi-fi, to avoid using up your data allowance (or incurring high mobile roaming charges if you’re overseas). 

1. Confirm your device is eSIM-compatible (most eSIM providers have lists of compatible handsets on their websites). You’ll also need to make sure it isn’t locked to a single network – for phones bought in the UK this is unlikely to be the case, as network locking has been banned by regulator Ofcom since December 2021. But if you have an older handset, there’s a chance it might still be locked to the network you bought it from.
2. Research the best eSIM plan for your needs from mainstream UK networks, or travel eSIM providers like Airalo, Holafly, or Saily, and buy your chosen option using their apps or websites. 
3. Follow the provider’s instructions to install the device on your phone, which it will send you by email or in-app. You’ll usually receive a QR code to scan, and a numeric code to enter manually if necessary.
4. On your device, go to Settings, then find and select the option to add a new mobile plan or eSIM.
5. Scan the QR code or enter the activation code manually.
6. Give the eSIM profile a clear label (e.g., “Australia eSIM”) to avoid confusion with your primary line and any other eSIMs.
7. When you’re ready to use your eSIM, adjust your device settings so that your eSIM will work properly. Select the eSIM as your primary SIM for data and/or calls (depending on what you’re using the eSIM for). If you’re using the eSIM abroad, you’ll also need to enable data roaming. 

If you’re buying an eSIM to use abroad, some plans only activate once the device connects to a network in the destination country — useful for travelers who want to install before departure but activate only on arrival.

Which Phones Support eSIM?

eSIMs have been a feature of many mobile devices for nearly a decade. The first mobile range with eSIM capabilities was the Google Pixel range; its handsets have had limited eSIM functionality since the 2017 Pixel 3a. Apple and other Android handsets joined the eSIM club over the next couple of years.

If you have any of the following phones, you can feel pretty confident that it has a fully supported eSIM built in:

• iPhones made since 2018 (the iPhone XS onwards)
• The 2019 Google Pixel 4 and later 
• Samsung Galaxy S, note and Z Flip models since 2020

A handful of the latest handsets don’t even have space for a physical SIM, relying entirely on eSIM functionality. These include older Motorola Razr models and the iPhone 17 Air. 

Older or budget Android devices may lack eSIM support, so check your specific model to see if it’s an eSIM compatible phone before you buy an eSIM plan.  

Benefits of Using an eSIM

• Speedy activation There’s no need to wait for a physical card to arrive or visit a store – eSIMs can be bought, installed and activated digitally, usually in a few minutes.
• Great for travel The fully-digital activation makes it easier to switch between networks if one has poor coverage, or add a travel plan while abroad.
• Multiple profiles You can store multiple eSIM profiles and have 1 or 2 active at the same time as your primary account.
• Second phone number Some eSIM plans include a phone number, meaning you can use two numbers at once (separate work and personal lines, for example).
• Extra security If your phone is stolen, the thief can’t remove an eSIM to disable tracking features, potentially making it easier to track your device down and get it back.
• Freed-up space Physical SIM trays take up valuable space inside a device; the freed-up space in eSIM-only phones can be used to pack in extra components (such as a bigger battery), or make the device itself more streamlined. 

Potential Drawbacks to Consider

• Not always portable Not every eSIM plan can be ported between phones, a potential frustration if you lose or upgrade your handset. And if your device breaks, you can’t physically move your SIM to a back up device. 
• Not available on some handsets Older and budget devices may not support eSIMs. 
• Potential activation issues Some eSIM users on Trustpilot have reported issues getting their eSIMs to work abroad. Issues are more common with some providers than others, so it’s worth checking reviews before you buy. 
• Can’t be removed This means that an eSIM-only device stays traceable/connected to the network by design – you can’t take it out to go completely off-grid.

Is an eSIM Safe to Use?

eSIMs are just as safe to use as physical SIMs. They use the same encryption and authentication standards as physical SIMs. And if your phone is lost or stolen, the account can usually be suspended or the profile removed remotely by the eSIM provider, similar to a physical SIM. The fact that eSIMs can’t be removed reduces some of the risk of an eSIM being cloned, as typically this requires physical access to a SIM.  

None of this means that eSIMs are completely free of security risks. eSIMs are equally vulnerable to malicious threats as physical SIMs, such as phishing, weak passwords, dodgy apps or malware, so it’s important to set strong security on your device and be on your guard against phishing attempts.