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what is an esim card - why esim cards are important -

Solving a connectivity issue, my experience with an eSIM.

In Connectivity, Digital Technologies by Scott

About this article:

Faced with a mobile phone line that was stuck in an unrecoverable state, and a phone number that was crucial for two-factor authentication, let alone business, I started looking for eSIM solutions and found This post looks at embedded SIM and how I solved my problem.
Embedded SIM Cards

What Is An eSIM Card?

In 1991 the first mobile phone SIM cards were the size of credit cards. Five years later the mini-SIM appeared, shaving almost 92% off the total size of the SIM card. Seven years later, the micro-SIM card appeared and nine years later even more compact, powerful smartphones with less space for SIM card enabling hardware ushered in the nano-SIM. The nano-SIM measures just 12.3mm by 8.8mm and can be found in most modern smartphones. The card's surface area is about two-percent of that of the initial full-size version that debuted 19 years before.

In 2016 the eSIM was introduced. The eSIM, or embedded SIM is a piece of embedded hardware (think "chip") that can be programmed remotely with the appropriate security, features and logic that you'd expect to find in a regular SIM card. The size of an eSIM is now typically 6mm by 5mm, and without the need for additional hardware, such as trays, sockets, gaskets, the actual amount of space, power and cost is significantly reduced.

Why is the eSIM important?

The reduced size, cost and power requirements that an eSIM can deliver compared to its predecessors enable smaller devices such as wearables (e.g. watches and biometric devices) and Internet of Things (IoT) devices to be connected via cellular networks.

It's not just those characteristics that make the eSIM attractive for those applications, but also the fact they can be programmed remotely, after installation.

As an example, the Volkswagen group can equip all their cars across all their brands with the same communications module, using the same eSIM technology. Then, they could, if they wish, connect the car to the local communication provider at the time of sale. For example, an executive level car manufactured in Germany, transported and sold in Italy could connect to WINDTRE, whereas an Audi Q5 manufactured in Mexico could connect to Telcel - all using the same embedded SIM card.

What about eSIMs in mobile phones?

Well, this is where this article started. Having recently moved from the UK to Slovakia, I had both a regular nano-SIM installed in my phone from a local operator, as well as an eSIM from a UK operator so I could keep and use my UK number.

This worked ok for a while, but when I tried to switch plans with my UK operator to avoid falling foul of the their EU fair use policy, something went wrong and my number became frozen and unable to be re-activated.

This was a major pain, not only because people couldn't get in touch with me, but many of my digital services are keyed to that number, along with many services like banking, doctors, and government websites that require that two-factor authentication via that number...all of which are much needed when finalising an international move.

(Apologies if you were one of the twenty-seven people who left me a voicemail during this time - I haven't been able to retrieve them, please call again)


Luckily I stumbled across which appears to be the only provider to offer pay-as-you-go eSIMs that you can buy online and have delivered digitally.

Even when I originally switched my UK operator service from a physical to embedded SIM, they needed to send me the activation code (a QR code) via snail-mail to a UK address. Apparently this is for security reasons, but frankly it seems archaic and just added effort, frustration and time to the process.

With, I was able to buy, register and have my sim card delivered, installed and activated in three minutes!

Yes, I timed it. 3 minutes to purchase, deliver, install and activate a sim card that gave me access to virtually any network in any country without roaming fees. Oh, and wait, it's also 5G enabled, too!!

Ok, so it's true, I don't get the cost efficiency of data bundles. With the eSIM in Slovakia a gigabyte (GB) of data will cost me €7. But actually that's not too bad because my traditional sim card on the local network gives me on just 3GB (plus calls and text) for €25/month.

However, compare that to what I was used to in the UK - unlimited calls, texts and 20GB of data for just £16/month - and there's still quite a disparity in pricing, but that's not why I use it.

Porting my number

It was also easy to port my old number over from the UK operator to the new embedded SIM from, meaning all my two-factor authentication now works again. If you left me a voicemail or tried unsuccessfully to contact me between 25th September 2020 and 7th October, please do try again 😀.

In summary

Embedded SIMs are enabling game changing technologies, like IoT, connected wearable and medical devices. They are also making it easier for consumers to switch mobile networks.

Switching networks is easier than many people think, and especially in the UK, porting your phone number, or in other words, keeping your number when you change operators is as simple as sending a text message and waiting a couple of days. Even though switching is easy, very few UK mobile consumers actually do it, which, when compared to the mobile operator brand's consumer strength and the increasing competition, is an interesting topic that I'll save for a future article that is already in the works.

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About the Author


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Scott is an Independent Technology Analyst, Content Writer and Connector of interesting people. Scott is a technologist at heart, with a history of technology innovation and marketing leadership roles. As the founder of this website and several other businesses, he is passionate about helping technology companies communicate their relevance and awesomeness in a way that engages and excites everybody. Get in touch with Scott here or connect with him on LinkedIn. Learn Scott's tips for content marketing, download his free template here..