What is an eSIM Card?

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What is an eSIM Card? Everything You Need to Know 

You may have come across eSIM cards as you shop for a new phone or may have seen them mentioned in some form of advertising and wondered what they are. eSIM cards don’t get nearly as much of the spotlight as other features do, despite the benefits and convenience they offer. 

Quick review: what is a SIM card? 

A SIM card, or "subscriber identity module," is a computer chip that holds your customer ID so your mobile service provider can identify your phone as yours. With this information, Optimum Mobile and other carriers can assign your phone number to your mobile phone device.  

When SIM cards were first released in 1991, they were the size of a credit card-and mobile phones back then were huge compared to the smaller phones today. SIM cards (and mobile phones) have come a long way since then.  

Today’s SIM cards come in two different forms: eSIMs and physical SIM cards.  

What's the difference between an eSIM and a physical SIM card?  

While you can remove a physical SIM card from your phone and move it into another one, an eSIM is hard coded directly into your phone through a chip. eSIMs can be programmed remotely, but they are built-in features of the latest generation of smartphones (as well as tablets, smartwatches, and other devices).  

You cannot physically remove your eSIM to move it to another phone, but you’re also not limited to only one eSIM per phone—the way you are with physical SIM cards.  

What are the benefits of eSIM? 

This new generation of SIM card technology offers many benefits compared to physical SIM cards. 

Easier to switch numbers. Instead of having to put in an order for a physical SIM card and wait for it to arrive in the mail, eSIM lets you switch numbers or even carriers with a phone call or online-from anywhere, anytime. 

Multiple SIM cards in a single phone. You no longer must carry a separate work and personal phone! With eSIM, you can access both lines on the same phone and just toggle between them, saving you from any hassle and the expense of multiple phones. 

Smaller SIM than ever before. While physical SIM cards have come a long way from their credit card-sized beginnings, eSIMs are embedded in the mobile device. This helps keep your phone lighter and makes more room for other functional features like a bigger screen or higher-capacity battery.

Options for a stolen phone. It can be possible to turn off eSIM cards remotely. This means that if your phone is lost or stolen, you could turn off your eSIM and prevent identity theft. 

International travel is easier. With eSIM, you can simply add international calling to your current phone, which works as soon as you arrive at your destination. Previously, you had to buy a separate physical SIM card when you traveled, and you had to keep a close eye on which country/countries your new SIM card could work. 

Can also support physical SIM card. If, for whatever reason, you are more comfortable with a physical SIM card, check to see if your phone can support one. If it does, you can always order and use a physical SIM card.   

What phones use eSIMs?  

Every major mobile phone manufacturer including Apple, Samsung, and Motorola have eSIM-ready phones, and the number of phones compatible with eSIM technology only continues to grow.   

You can search our current list of available phones for the latest details on what eSIM-ready phones we Optimum sells. 

Some mobile phones let you use both physical SIM and eSIM, while others let you toggle between the two different types. 

How do I activate my eSIM?  

Are you ready to activate your phone with eSIM? First things first: you will want to connect to WiFi in order to complete certain activation steps. 

From there, the steps to activate your eSIM will depend on your device manufacturer as well as factors like whether you're transferring your number. Optimum Mobile makes it easy with activation guides, or you can reach out to our Support team to get one-on-one assistance. 


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