What Is eSIM? What You Need To Know…

By Michael Grothaus •  Updated: 01/05/21 •  5 min read

For almost as long as there have been mobile phones, including iPhones, there have been SIM cards. SIM cards are those tiny pieces of plastic with a golden chip printed on them that we insert into our smartphones.

iPhones run SIM Cards and so too do Android phones. Even old school brick phones like the Nokia 3310 ran SIM Cards. To connect to a network, you need a SIM.

And your SIM will have a unique ICCID and IMSI number that relates to its country of origin and the networks it is authorised to connect to.

But recently the age-old, humble SIM card is being usurped by a new variant–the eSIM. Here’s what you need to know.

What Is A SIM Card?

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A SIM card is that tiny plastic card with a golden chip printed on it. SIM stands for subscriber identification module and the cards have been around since the early 1990s. However, with the mass adoption of smartphones in the mid-2000s their use exploded. Today, SIM cards are a necessary component of any smartphone–at least if you want cellular and data access via the phone.

Depending on how old a phone is, it could require a different0sized SIM. Matter of fact, there are currently four physical types of SIM cards. They are:

What Info Does A SIM Card Contain?

SIMs contain information like your phone number, other unique identification numbers like ICCIDs and IMSIs as well as IANs and EANs. These numbers all help identify your SIM and link your cellular data plan to that SIM card, thus enabling internet access on the smartphone your SIM card is in as well as cellular and text services.

SIM cards also carry a limited amount of storage capacity. The max is 256kb–not much at all. But because of this capacity, SIMs can contain things like your phone contacts, although today those are more likely to be saved in a user’s cloud account.

Finally, a SIM also contains a PIN number, which lets you lock it and helps prevent anyone from gaining access to your phone number and service should they steal your SIM. Finally, a SIM contains a PUK number, or personal unblocking key. This is a security measure that prevents unwanted SIM access.

How Is An eSIM Different?

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An eSIM is different than a SIM because there is no physical SIM card the user obtains that they need to insert into their smartphone. eSIM stands for embedded-SIM, which means it’s already built into the phone you bought.

eSIMs are the new frontier and the future of SIM tech for several reasons:

This last point is a big deal because it makes international traveling much easier. Now when you land in a new country, you no longer need to rush to the airport kiosk to swap out your SIM with a local SIM. Instead, you could just use a local carrier’s app to get a temporary phone and data plan for the country you are in. Pretty cool.

Are eSIMs Better Than SIMs?

Yes. The fact that they do away with any kind of physical card makes them both easier to manage and more secure.

What Phones Have eSIMs?

What Is eSIM? What You Need To Know...
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Many phones have eSIMs nowadays. Matter of fact, many flagship smartphones have both a regular SIM slot and an eSIM built-in, making them dual-SIM phones. This allows one phone to have two different phone numbers.

Apple iPhones that offer eSIM support include:

Android phones that have eSIM support include:

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Michael Grothaus

Apple expert and novelist, Michael Grothaus has been covering tech on KnowYourMobile for the best part of 10 years. Prior to this, he worked at Apple. And before that, he was a film journalist. Michael is a published author; his book Epiphany Jones was voted as one of the best novels about Hollywood by Entertainment Weekly. Michael is also a writer at other publications including VICE and Fast Company.
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