What is an eSIM? Here’s everything you need to know

Mark Jansen
Guide to the eSIM

The humble SIM card has survived for quite a while, but it now finally looks like it’s on its way out. Why? Well, the eSIM, a much smarter technology, is here to save the day.

Before we dive into what an eSIM is, it might be helpful to understand what a SIM is. A SIM, which stands for “subscriber identity module,” basically contains the information that authenticates your identity to a carrier. In other words, the SIM card is what tells a carrier that you’re you — and without it, carriers wouldn’t know that you’re subscribed to their network, and thus wouldn’t let you use their cell towers.

But learning about a standard SIM card isn’t why you’re here. New phones like the Pixel 4, iPhone 11 Pro, and Motorola Razr boast of eSIM support, so it’s a good idea to know exactly what that means. Here’s everything you need to know about the new eSIM.

What is an eSIM?

An eSIM is exactly what it sounds like: An electronic, or embedded, SIM. Instead of a physical card, SIM technology is built right into your phone. It’s a small chip that’s used to authenticate your identity with your carrier.

Of course, you probably have some questions about that. When traveling with a traditional SIM card, you may have to swap to another carrier’s SIM card to keep your coverage. If you want to change carriers at home, you’ll also have to physically replace your SIM card. With that in mind, does a built-in SIM mean you have to switch phones? Thankfully, no. In fact, one of the advantages of eSIM technology is that it makes it much easier to switch carriers. Instead of having to order a new SIM and wait around for it to arrive, you can switch to a new carrier straight from your phone. If you’re a dual-SIM user, eSIM technology supports multiple accounts — and switching between them is super easy.

With an eSIM, your phone has a few new settings devoted to your SIM card that allow you to switch between lines and carriers and manage accounts. The Google Pixel 2 was among the first phones to support eSIM technology, and an app for managing your eSIM is available from the Google Play Store. Then, the iPhone XS came out, and it offered both a physical SIM card and an eSIM as a secondary, though the eSIM was only enabled later down the line through an iOS software update. Unfortunately, the Chinese version of that iPhone did away with the eSIM altogether — instead offering a dual-SIM slot (a practice continued with the iPhone 11). That could suggest that Chinese carriers are less interested in adopting the new tech, which is bad news for those who were looking forward to using an eSIM to travel to China.

The eSIM is helpful for another reason: It helps make devices smaller. Now, that may not matter all that much for phones (although a little extra room for battery capacity is always nice), but it could be extremely helpful for wearables. The Apple Watch Series 5 and Series 4 already have eSIMs, and that helps Apple keep the overall size down, which is vital for something you wear on your wrist.

When can I start using an eSIM?

It may be a while before the full potential of the eSIM is realized, but you can take advantage now with the right phone and service. Some handset manufacturers, like Apple and Google, have adopted eSIM tech, and many major carriers around the world support eSIM service already. In the U.S., for example, you’ll find eSIM support at AT&T, T-Mobile, Verizon, Truphone, and Ubigi. Apple provides a regularly updated list of participating carriers worldwide, and it’s encouraging to note that the list is growing all the time.

Going forward it’s likely that eSIMs will find a home in a new generation of LTE-connected computers. Those computers first started coming out in 2018, although you should expect to see a lot more of them in the next few years.

Slowly but surely, eSIMs will take over. If your carrier supports it, and your phone supports it, then that may be all you need to start using the new technology today. To help bridge the gap, some phones with eSIMs still have traditional SIM card slots, but eventually, those trays could go away altogether.