Updated: Apr 30
A SIM – traditionally a small plastic card that slots into your mobile phone –is an acronym for ‘subscriber identity module’.
It holds information, such as your mobile number, and allows you to make and receive calls and texts, and use data on your phone.
SIMs can also store contacts and phone numbers which makes switching phones easy – you can simply take your SIM out of your old phone and slot it into a new one.
What is an eSIM?
But so-called eSIMs are designed to supersede old-style physical SIMs (and, in case you’re wondering, the ‘e’ stands for embedded).
Instead of being a removable plastic card inside your phone, an eSIM is a small chip embedded in your handset. You can’t remove it and put it in another phone.
The information on an eSIM is rewritable. This means you can change your network without removing your SIM and inserting a new one.
A time when eSIMS completely replace plastic SIMs is probably still quite some way off. At the moment eSIMs are more commonly used as the second SIM in a dual-SIM handset.
What are the advantages of an eSIM?
It’s easier to switch networks. An eSIM makes it much easier to switch mobile networks. Instead of needing to order a new SIM, waiting for it to arrive, then inserting it into your phone, you can switch to a different network with a phone call or online. You also won’t need to go hunting for a SIM ‘ejector tool’ to remove the old SIM from your phone.
You can temporary change to another network. Up to five virtual SIM cards can be stored on one eSIM at a time. This means you can quickly switch between different networks if you find yourself in an area without a signal on your usual network.
It also makes it easier switch to a local network while travelling, without needing to physically insert a local SIM. Using a local mobile network while abroad can be much cheaper than paying roaming costs to your UK network. Not removing your UK SIM from your phone will also reduce the risk of losing it.
Allows you to have more than one SIM. eSIMs also offer the same advantages as dual-SIM phones with two slots for traditional plastic SIMs, the most obvious being that you can have two phone numbers on one device.
This can be handy if you want one number for personal use and another for business – but you don’t want to carry two phones around. You’ll be able to receive phone calls and texts on both numbers all the time and choose which SIM to use for making calls, sending text messages, or using data.
Uses less physical phone space. Another advantage of eSIMs is that they will eventually negate the need for a physical SIM card and its tray. Smartphone manufacturers could potentially use this space to increase a phone’s battery size or add more features to a handset. Fewer holes in a handset also mean more protection from moisture and dust, so less breakdowns.
There’s also the potential to make handsets smaller in some cases. But the real space advantage is for wearables such as smartwatches, as people don’t want to wear an enormous device on their wrist. The Apple Watch Series 5 and Series 4 already have eSIMs, as do Samsunggear S2 and Gear S3 smartwatches.
What are the disadvantages of an eSIM?
There are a couple of potential downsides to eSIMs, though.
Not as easy to quickly switch devices. Right now, if your handset stops working you can easily remove the SIM and put it in another phone, keeping your number and contact information (if your contacts are stored on the SIM).
This will be much trickier with an eSIM – although storing information and contacts in the cloud is designed to make it easy to transfer data such as contacts from one phone to another.
Nowhere to hide. You also can’t remove an eSIM from a device, which may be viewed as a downside if you have concerns about your movements being tracked. But this may also be an advantage as it means phone thieves cannot easily hide the location of a stolen phone.
Do all smartphones have an eSIM?
At the moment only a handful of the most recent smartphones and wearables have an eSIM. These include:
All of Apple’s latest iPhones – the iPhone XS, iPhone XS Max and iPhone XR, plus the new iPhone 12 range, and the iPad Pro
Samsung’s Galaxy S20, S20+ and S20 Ultra
The Google Pixel 3 and 3 XL
Motorola’s Razr (only an eSIM, it doesn’t have a physical SIM card)
Samsung Gear S2 and Gear S3 smartwatches
Apple Watch Series 3, 4 and 5
Do all networks support eSIM?
Not all networks support eSIMs – but they will do in time when this technology becomes standard.
In the UK, EE, O2 and Vodafone all currently support eSIMS in some capacity.