We could see phones and networks adopt electronic SIM cards for future smartphones - essentially removing the need to have a physical SIM card (and SIM slot). Apple has now turned to eSIM to add connectivity to the Apple Watch Series 3

The use of eSIM brings a number of advantages to device manufacturers, but there's also some advantages for the user too.

But what exactly is an eSIM? And what exactly will it offer if your next device supports it? Let us explain...

The term "eSIM" relates to a new standard being promoted by the GSMA - the association that represents network operators worldwide.

It will come in the form of an integrated SIM, one that cannot and need not be removed from a device - something that consumer electronics manufacturers are also keen to adopt for connected items around the house as part of the Internet of Things, and something that's been used by some car manufacturers too.

The information on it will be compliant or rewritable by all operators, meaning a user can decide to change operator with a simple phone call. A new SIM will not be required, nor should there be any time delay in switching the eSIM to its new purpose. There will also be no physical swapping over required by the user.

That was the original premise of the eSIM, but one of the advantages it offers from a design point of view is that you make a smaller device because there's no need to accommodate a SIM card or the tray that holds it, hence the use in devices like the Apple Watch 3.

With the announcement of the Apple Watch 3, Apple confirmed that the new connected version of the watch will be using an eSIM. It will be on the same number as your iPhone, so there will be a seamless experience across the two devices. For the Apple Watch 3, that means you can use messaging services, place calls, use mapping or stream music without your phone. 

The important thing about eSIM, however, is that it needs to be supported by the network or carrier, meaning the Apple Watch 3 will exclusive to some carriers in some countries. For the UK, that network is EE.