If you've picked up a new phone in the last couple of years, you've probably noticed there's no SIM tray to fiddle with anymore. That's because eSIM technology is quickly replacing the plastic SIM cards we've relied on for decades. Let’s dive into what an eSIM is, how it works and why it might be worth switching to one.

An eSIM (embedded SIM) is a digital SIM built directly into your device rather than a physical card you insert. Instead of popping in a piece of plastic, your network profile is downloaded straight onto a small chip already fitted inside your phone, tablet or smartwatch. It does the same job as a traditional SIM – connecting you to your network so you can make calls, send texts and use data – it's just stored differently.

The shift matters because it removes one step of getting a new device up and running. There's no tiny tray to eject, no PIN to lose and no card that can be dropped down a drain mid-house-move. For anyone who's ever misplaced a SIM PIN at the worst possible moment, that alone is a good enough reason to pay attention.

Your network sends a digital SIM profile to your device, usually via a QR code or directly through an app like My O2. Once that profile is installed, your phone behaves exactly as it would with a plastic SIM, connecting to the network, holding your number and letting you use your plan as normal.

Each eSIM is tied to a unique identifier called an EID, which means it can't be removed or transferred to another device the way a physical SIM can be pulled out and swapped. If your phone is lost or stolen, your eSIM and the information on it stay locked to that device rather than being up for grabs. Many modern devices also support dual SIM with eSIM, letting you run two numbers at once, such as a personal and work line, without carrying two phones.

O2 eSIMs are available across Pay Monthly, SIM Only and Pay As You Go plans on all compatible devices. Most recent flagship phones support it, including iPhone 18 Pro Max, iPhone 18 Pro, Samsung Galaxy S26 Ultra, Samsung Galaxy Z Flip8 and Google Pixel 11 Pro XL. If you're upgrading to any of these, you can choose eSIM at checkout and it'll already be installed and ready to use when your device arrives.

Not sure if your current phone is compatible? Dial *#06# from your dialler and if you see an EID listed alongside the barcode, your device supports eSIM. If you're already an O2 customer on a physical SIM, most devices let you switch by finding the 'Convert to eSIM' option in your connectivity settings, so there's no need to wait for an upgrade to make the change.

Rather than hunting for a local SIM card at the airport or paying inflated roaming charges, many travellers now add a second eSIM for their destination country and keep their UK number active on the same device. It means you can land, connect and carry on using maps, messaging and calls without any of the usual holiday admin.

An international eSIM is particularly handy for regular travellers or anyone working across multiple countries, since it removes the need to swap physical SIM cards every time you cross a border. O2 customers travelling within the EU can also make use of inclusive EU roaming on eligible plans, so it's worth checking your allowance before you consider adding a separate travel eSIM for a trip.

Whether a Pay As You Go or Pay Monthly plan suits you best really comes down to how you use your phone. A Pay As You Go eSIM is a solid option if you want flexibility with no ongoing commitment, topping up only when you need to. A Pay Monthly eSIM contract, on the other hand, tends to work out as better value if you use a consistent amount of data each month and want the reassurance of a fixed monthly cost. 

If you're weighing up the best eSIM for you, our SIM Only deals are worth a look with a range of data allowances and contract lengths to suit different usage habits, all available as an eSIM at checkout.

Getting started is more straightforward than it sounds. If you're on a new Pay Monthly device, your eSIM is usually pre-installed and activates automatically when you switch your phone on for the first time. If you've ordered a SIM Only plan or you're switching an existing device, you'll be sent a QR code through My O2. Connect to WiFi, open your camera app in photo mode, scan the code and follow the prompts on screen. Most activations complete within a few minutes.

For a full walkthrough, including device-specific guidance for Apple and Android, our eSIM help guide covers everything from installation to moving your eSIM between devices.

For most people, the answer is yes. It's quicker to set up, more secure if your phone goes missing and useful for anyone who travels or wants two numbers on one device. As more manufacturers move away from physical SIM trays altogether, there's a good chance your next phone will be eSIM-compatible.

Check out our eSIM deals