What's an eSIM and why is it important for the future of mobile?

Visible SIM card next to Pixel 3a
Visible SIM card next to Pixel 3a (Image credit: Ara Wagoner / Android Central)

Best answer: An eSIM integrates the functions of a SIM card into a phone's hardware, making it easier and quicker to change phone service. Using an eSIM can also make it easier to manage multiple phone services on one device.

What is an eSIM?

For those asking, "What is an eSIM and why is it important?" Most phones sold today, and in the past several years, come with a SIM card is included or provided by your carrier to tell the phone how to connect to the network and what service it gets. These SIM cards look like small memory cards and usually slide into the side of your phone on a small tray. However, companies like Google and Apple have recently started to push an embedded SIM, or eSIM, as a better solution while still keeping a SIM card slot for compatibility.

A carrier can activate this eSIM to receive service without getting a specific SIM card from the carrier. Your eSIM could either be activated remotely by the carrier and, in some cases, could even be done automatically. Many of the best cell phone plans support eSIM though you may need to contact the carrier to get your eSIM information.

Why would I want an eSIM?

One of the biggest reasons someone would want to have an eSIM is easy access to new phone plans. In addition, some carriers provide phone service in an app and can activate services through your eSIM while you travel. This can allow you to keep your phone active on your standard line without risking massive roaming fees.

Some people may also want to have multiple numbers active on one phone. This can be great for someone who wants to manage a business phone number and a personal number simultaneously. It can also be a big help for someone who wants to make sure they have a solid connection in more places, thanks to accessing multiple networks. Google Fi can even use the eSIM with a standard SIM in the Pixel 4 or newer to improve its service coverage. Pixel 4a 5G and Pixel 5 even have access to 5G coverage with the dual SIM feature.

Galaxy S20+ 5G network with SIM cards

Source: Samuel Contreras / Android Central (Image credit: Source: Samuel Contreras / Android Central)

Having access to an eSIM in other devices such as smartwatches, tablets, or even notebook computers can make it easier to have data on those devices without worrying about which carrier you will use. Also, removing a physical opening in the side of a phone can improve water resistance since current SIM trays rely on a gasket to keep water out. If it doesn't get seated properly or deteriorates, water can get in.

One of the main arguments against eSIMs is that people are afraid carriers will use the technology to lock phones out of activation on other carriers. While there is some plausibility to this, the end-user can now erase their eSIM on their own, making it possible to activate on another carrier.

When Samuel is not writing about networking or 5G at Android Central, he spends most of his time researching computer components and obsessing over what CPU goes into the ultimate Windows 98 computer. It's the Pentium 3.

  • The only reason I'm against eSIM is because of carriers, not the technology. Historically that is how CDMA IS-95 and cdma2000 worked, where the subscriber identity is on the phone itself or on a R-UIM just like GSM based standards. But it was carriers that decided to start using whitelists and make them artificially not interoperable, and I would not put it past them to not do the same with this.
  • I am wary of eSIM because it will probably mean the end of multiple-SIM phones and add complexity to changing phones. For example, if I had expensive eSIM phone and I wanted to take a cheaper eSIM phone while going out how is that done? How can I borrow a buddy's phone and use it if it is eSIM? How to prevent remote hijacking of phone number if there is no physical SIM needed to validate proper ownership? Much of the eSIM benefits could be worked out with other ways.
  • Would an unlocked phone even exist in this system?
  • I would imagine so. I imagine you would simply have to call your service provider and give them whatever information they need to activate the device. That's my issue. When I switched from my Note4 to my Note8, I had to visit my carrier for a nano SIM. (I wasn't comfortable cutting the micro SIM to fit.) I would much prefer to simply pop out the SIM card from one device and pop it into another one then have to waste time dealing with customer service anywhere. Plus, you can save some things on a SIM card so it is swapped between devices. How would this work with an eSIM?
  • And I'm sure carriers will be very helpful in transferring your eSIM profile, should you ever decide to switch.
  • As long as you aren't switching providers, I don't see why they wouldn't be.
  • Not in favor of eSim as I Remer being locked to a carrier in the AMPS and CDMA days and forced to used expensive roaming when traveling. What of dual SIM phones, will they still exist?
  • I'm against eSim because if I wanted to switch carriers, I would have to get another Samsung Gear S3 Frontier because I can't take my T-mobile Gear S3 to Verizon or AT&T since they have it on lock even if you found a way to unlock it apparently.
  • I'm against this, I feel with countries forcing carriers to sell there phones unlocked, this would be a step backwards.
  • You got one thing wrong. You said "If you travel, for example, getting access to a new country's mobile provider won't require tracking down and swapping out SIM cards."
    That should be "If you travel, for example, getting access to a new country's mobile provider you're not able to swap out SIM cards. This is a problem not a feature.
  • Well, I imagine if you travel abroad, you would give a foreign service provider whatever information they need to activate your device on their system, and you would go through system settings to swap between providers as you need to, instead of swapping cards.
  • Nothing good will come of this. It has no benefits for the extreme majority of people, and carriers would abuse it. Also a privacy and inconvenience risk.
  • This!