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What is an e-SIM: Everything you need to know

28th September 2018

Phones have been using SIM cards for years and while they’ve got smaller over time and added support for newer mobile technologies the concept of the SIM card hasn’t really changed.

But it might be about to, as a new thing called an e-SIM or eSIM could be at the heart of smartphones in the near future, and even now we're starting to see them in a few phones such as the iPhone XS.

Here's everything you need to know about this exciting evolution of the SIM card.

What is an e-SIM?

An e-SIM is an embedded SIM card, meaning that unlike current SIM cards you can’t take it in or out of the device. That might sound like a bad thing but it’s designed so that you don’t have to, as rather than being locked to a specific network the SIM card can change network when you do.

What’s so good about it?

At a minimum it will take some of the hassle out of changing networks, plans and devices. No longer will you have to wait for a new SIM card, request a PAC code and wait for your device to change over. Instead you just request the move and your SIM card will automatically be set up on your new network or plan.

While if you buy a new device you just register it to your account and it will automatically be set up with your previous number and details and you won't have to worry about the various different SIM card sizes we have today. When 5G arrives there’s also a high chance that you’ll be able to switch from a 4G tariff to a 5G one without needing a new card.

It could even mean the freedom to change network as and when you choose, though in practice the mobile networks are likely to still lock you into contracts.

Multiple networks and numbers can be stored on a single eSIM too, so you can have more than one number. This could be handy if for example you want both a work and personal number on one phone, or if you’re travelling abroad and want a local number to avoid roaming fees.

Plus, if phone-makers can remove the SIM card slot they can save a little bit of space, especially as an eSIM itself is smaller than a nano SIM. That means there’s more room for other components or for example a slightly bigger battery. The saved space will be tiny, but then so are some smartphone components.

Alternatively, that saved space could be used to make a device smaller, and by not having a physical SIM card phones will likely become less popular targets of theft, since thieves won’t be able to remove the SIM card and replace it with a new one.

Are there any downsides?

Any e-SIM depends on networks supporting it. It’s unlikely that they’ll be widely rolled out before most or all networks agree to support them, but if any networks do hold out then you may be unable to use them if you have a device with an e-SIM.

When can I get one?

You can already get devices with eSIM cards, though not many. The latest and most high-profile example is the Apple iPhone XS, iPhone XS Max and iPhone XR. However, these also have a standard SIM card slot as well, since many networks don’t yet support eSIMs.

This isn’t Apple’s first foray into eSIM cards either, as the company also previously put one in the Apple Watch 3 (and now the Apple Watch 4) and various iPad models, though it used to call it an Apple SIM.

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Samsung has also dabbled with eSIMs, though not yet in phones, putting one in the Samsung Gear S2 and Samsung Galaxy Watch.

At the moment, the usefulness is limited as not all networks are on board. For example, the Apple Watch 3’s eSIM only works with EE and Vodafone in the UK, while so far EE is the only network to have confirmed it will support the eSIM in the latest iPhones, but we expect wider compatibility as the tech becomes more popular, and putting it an iPhone is a sure way to boost popularity.

Handily, the GSMA has now agreed upon a standard for eSIMs, which is another thing that should help push them out in to the mainstream, since the tech will be much the same whatever phone you go with.

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