What’s an eSIM?

An eSIM -- that stands for "embedded subscriber identity module" -- could be a tiny electronic chip within a phone that serves a similar function because of the tiny plastic SIM cards we've used for years. while not a SIM card, your phone does not understand that carrier to connect to or your telephone number, and your carrier does not understand that phone to produce service to.

Unlike carrier-locked SIM cards that restrict you from switching between carriers, an eSIM can be programmed and reprogrammed as needed, allowing you to hop between carriers or cancel and start service without having to get a new SIM card each time. 

Without a removable SIM card tray and the precious space that it requires, phone makers will be able to squeeze larger batteries inside a phone's housing or use the extra space for additional cameras or new features. Of course, no SIM card slot likely means no microSD card slot for adding additional storage, a change that phone-makers are also migrating toward.

The eSIM is still young, and as such the process for things like activation and support from carriers and phone makers will need to be streamlined (more on both of those aspects below), but one thing is clear: One day soon, we'll be able to instantly switch between carriers with just a few taps on our phone's display. 

Apple's iPhones that have two SIM cards an eSIM and a physical card can connect to two different carriers and phone numbers at the same time. So you can have your personal and work number on one iPhone, even if you have T-Mobile and Verizon Wireless, respectively, as providers. This is possible on an iPhone because it's unlocked and supports multiple carriers.

Phones with eSIM are also handy for frequent travelers out of the country. You can use the eSIM to sign up for a data plan overseas and save yourself from roaming fees. And, if you set up an eSIM through a provider like GigSky before you leave, you'll have data access as soon as you land. Of course, you don't have to use both SIM cards at the same time, or even at all, and when you buy the phone from your carrier, it usually comes with a standard SIM already installed and ready to connect to your account.

However, if you buy a phone that doesn't come with a SIM card from select retailers or websites like Swappa, for example, you need to visit your carrier or order a SIM card and wait for it to arrive in the mail, then get it activated. With an eSIM, you don't have to wait you can activate the phone in just a few minutes.