eSIM or embedded SIM cards are common nowadays; however, not everyone uses them. The traditional SIM cards we mainly use are plastic-made SIM cards that come in different sizes.
eSIM is a circuit board that is embedded inside a 2G, 3G, 4G or 5G cellular device by phone manufacturers that can be programmed to a particular mobile network using a QR code; a physical SIM is detachable and built as a metallic chip on a piece of plastic that can be manually inserted into a phone.
While you can have a fully functional mobile phone with just an eSIM inside it, the mobile phone manufacturers build eSIM as a secondary SIM in smartphones. Generally, smartphones have a physical SIM slot for the primary SIM where you can insert a plastic-made micro or nano-SIM card.
The phones with two SIM slots can take in two separate SIM cards and are therefore called dual-SIM phones. As mobile phones and other cellular devices such as smartwatches continue to evolve, eSIM is becoming a popular option to add the SIM capability.
If you are new to the concept of dual-SIM phones or just want to learn more, please have a look at my dedicated post on dual-SIM phones with eSIM and physical SIMs.
What is the difference between an eSIM and a physical SIM?
An eSIM is an embedded SIM where the SIM hardware (chip) is built inside compatible cellular devices that you can programme to any mobile network using a QR code. A physical SIM is a regular plastic-made SIM card available in standard/micro/nano sizes that you can manually insert into your phone.
A SIM or Subscriber Identity Module is an integrated circuit traditionally built on a piece of plastic and can be inserted into any compatible mobile phone. While CDMA-based mobile networks, including cdmaOne and cdma2000, do not have detachable SIM cards, GSM, UMTS, and LTE networks have always relied on physical SIM cards.
Over the years, we have seen a gradual reduction in the size of plastic SIM cards, and we now get a triple SIM that includes all possible SIM sizes, including standard, micro and nano, built as one SIM card. So, depending on your mobile phone, you can choose the required size that fits your phone.
If you are ordering a SIM card from a GSM/UMTS/LTE mobile operator, you are expected to receive a triple SIM card with all three SIM sizes built into the standard SIM. With a triple SIM, a user gets one standard-sized plastic card where the chip (the metallic golden thing) sits in the middle, but the plastic around the chip is cut out in a way that allows a user to adjust the SIM size, as shown in the picture below.
On the other hand, with an eSIM, you do not need to worry about the SIM sizes because you just need to download the SIM software on your eSIM-compatible mobile phone. eSIM compatible means that the eSIM hardware is already inside your mobile phone. eSIM requires you to use your phone camera to scan a QR code provided by your mobile service provider to download the SIM.
Generally, all eSIM-capable smartphones also have a physical SIM slot for a nano-SIM card. The physical SIM slot is for the primary SIM, whereas the eSIM is the secondary SIM. You, however, do not necessarily require a physical SIM for your phone to function.
Is it better to use an eSIM instead of a physical SIM?
If you only want to use an eSIM and no physical SIM, your smartphone will still function properly. Depending on your preference, you may use an eSIM instead of a physical SIM, and the phone will work fine without needing to rely on a physical plastic SIM card.
Since both eSIM and physical SIM require circuitry and software, there is no difference in how they function once they are inside a mobile phone. The key difference is that the circuitry for an eSIM is already embedded inside the phone. In contrast, with a physical SIM, the circuitry is built on a detachable piece of plastic.
eSIM is the evolution of the existing SIM technology as it gives more control to the customers by allowing them to remotely programme the embedded eSIM to register with any mobile network operator of their choice.
Furthermore, as the telecom industry welcomes new cellular device types such as cellular IoT devices, smart metres, smartwatches and other wearables etc., relying on less detachable hardware (plastic SIM and SIM tray) will make the lives of customers and device manufacturers easier.
eSIM offers more flexibility to the cellular device manufacturers to embed the eSIM chip wherever they see fit without creating a separate space for an easily accessible SIM tray for a physical SIM. For customers, this means they do not have to look for the SIM tray or the SIM card ejector to insert or replace their SIM.
Advantages and disadvantages of using eSIM
|Switching from one mobile operator to another||eSIM allows a SIM to be delivered digitally, making it easier to switch from one mobile network operator to another.||Currently, when you start a new eSIM contract in the UK, the service provider still physically delivers the eSIM pack. A fully digital onboarding journey is yet to be realised.|
|eSIM in the UK is only available on pay-monthly phone plans||If you already have a pay-monthly phone plan in the UK, you can contact your mobile service provider to swap your phone plan from a physical SIM to an eSIM.||In the UK, eSIMs are not available as pay-as-you-go (prepaid) SIMs, which means you need a pay-monthly plan for your eSIM.|
|eSIM gives you an additional phone line||eSIM today is embedded in mobile phones as an “additional” SIM slot that offers customers the benefit of dual-SIM phones.||Cellular devices like smartwatches that only rely on eSIM (and no physical SIM) have one phone line.|
|eSIM takes less physical space in your phone||eSIM hardware (chip) is built directly into the mobile phone, which takes less space than a physical SIM compartment. That enables the device manufacturer to use the extra space for other components, e.g. an additional SD card.||Since most eSIM capable mobile phones today also have a physical SIM slot, the overall space-saving achieved through eSIM is debatable. However, if you compare an eSIM capable phone with other dual-SIM phones, there is an obvious space-saving.|
|You must be connected to Wi-Fi when downloading and installing an eSIM||If you have an active Wi-Fi connection, eSIM can save you the hassle of using a SIM ejector tool to insert the SIM manually.||If you are travelling and do not have access to a Wi-Fi network, you won’t be able to download an eSIM on your phone. In situations like those, you are better off with a plastic SIM which is much easier to insert into a phone.|
|No need to worry about old and new SIM cards||With an eSIM, when a new cellular technology, e.g. 5G, is introduced, you don’t need to worry about procuring a new SIM card from your service provider. Since the required hardware for eSIM is already built into the phone, it is much easier to transfer the eSIM digitally to the new phone.|
Switching from one mobile operator to another
In theory, eSIM makes it easier to switch networks, but it may take some time for this theory to become a reality. Currently, in the UK, when you buy a new eSIM contract, you receive the eSIM pack physically delivered to your home address.
If you already have a SIM plan with a service provider, the ease of switching to an eSIM is limited to swapping your existing plan from a physical SIM to an eSIM. While this can be achieved in a few minutes rather than hours or days, the switching between two different service providers is not made faster by eSIM.
eSIM in the UK is only available on pay-monthly phone plans
When switching from one mobile service provider to another, one key consideration is the contract type. Unfortunately, in the UK, most mobile service providers do not offer the eSIM option on prepaid subscriptions and require you to have a pay monthly (postpaid) subscription to qualify for an eSIM. Since getting into a long-term postpaid contract is a bigger decision than getting a prepaid SIM, eSIM currently does not make it any easier to switch service providers.
Gives you an additional phone line
While this may change over time, currently, eSIM is built into mobile phones as an additional SIM rather than the primary SIM, which essentially turns an eSIM capable phone into a dual-SIM phone.
Smartphone manufacturers embed the eSIM hardware inside the phone as an extra SIM, but they are still also building a physical SIM slot that you can use with a plastic SIM to enjoy two phone lines potentially. You can use one phone line for your primary number and the other as a backup. You can keep both profiles on the phone and switch when needed.
Since mobile operators in the UK only offer eSIM as a pay-monthly subscription, you can move your pay-monthly subscription to an eSIM and use the physical SIM slot for a prepaid (pay as you go) SIM to enjoy the dual-SIM benefits without having two pay-monthly contracts.
eSIM takes less physical space in your phone
A benefit of eSIM that people mostly talk about is that it takes much less physical space in your phone. However, this benefit is only valid if you buy a device with only an eSIM slot and no physical SIM slot or if you are in the market for a dual-SIM phone where one SIM slot is an eSIM.
The eSIM capability also benefits the device manufacturers because creating an eSIM instead of a physical SIM compartment saves space in a device which can be used for adding other components to the device, e.g. an SD card.
The eSIM technology goes beyond mobile phones and supports all types of cellular devices. If a device manufacturer can save physical space due to the eSIM capability, they are in a better position to build their devices more smartly. eSIM is an excellent option for wearables like smartwatches, where not requiring a physical SIM slot can lead to design benefits.
You must be connected to Wi-Fi when downloading an eSIM
While eSIM is the future as it can potentially make it much faster to deliver the SIM electronically to a customer, there may be some potential limitations. When installing an eSIM on your phone, you need to be connected to the internet.
Downloading the eSIM on a mobile phone is relatively straightforward by scanning a QR code if you have internet connectivity available. However, if you are travelling or in an inconvenient location without reliable Wi-Fi, you may struggle to download and install the eSIM on your phone. That is where the traditional plastic SIM comes in handy, which is much easier to manage by simply inserting the plastic SIM into the SIM compartment of the phone.
No need to worry about old and new SIM cards
A SIM card is a combination of the SIM hardware (the physical chip) and the software that contains your subscription information. eSIM decouples the hardware and the software and allows the customers to buy the SIM software separately, which they can install using a QR code.
When a new cellular technology gets introduced (e.g. 5G), one of the first questions people ask is if their old SIM card would work in their new phone. With an eSIM, this question goes away because the SIM hardware is built directly into the phone, so there is no such thing as an “old” SIM anymore.
With an eSIM, when you buy a new phone that works with new cellular technology, e.g. 5G, you can be sure that the eSIM hardware is compatible too because it is built by the same manufacturer that makes the phone. All you need from your mobile operator is the software for the SIM that you can install using a QR code.
How can you get an eSIM for your phone?
If you want to use eSIM on your mobile phone, your device and service provider must support the eSIM technology. For a customer, there are two aspects to the eSIM technology:
1 – eSIM hardware
The hardware for eSIM is built directly into a mobile phone which makes the phone eSIM capable. You can check a phone’s technical specifications before buying it to ensure it is eSIM capable. If you already have a phone, you can check for eSIM support in your device’s “Settings” menu. I have written a dedicated post on how to find out if your phone supports eSIM.
2 – Programmable software for eSIM
When you buy a regular plastic SIM, it is provided by your mobile operator or service provider. With an eSIM, your mobile operator or service provider sends you an eSIM pack that includes a QR code and an activation code.
If your mobile phone supports the eSIM technology, it can use your phone’s camera to scan the QR code to programme the eSIM hardware already embedded in your phone. The eSIM pack also includes an activation code that you can manually enter during the eSIM set-up process in case you struggle with the QR code. Have a look at my dedicated post with screenshots to find out how to download your eSIM.
Here are some helpful downloads
Thank you for reading this post. I hope it helped you in developing a better understanding of cellular networks. Sometimes, we need extra support, especially when preparing for a new job, studying a new topic, or buying a new phone. Whatever you are trying to do, here are some downloads that can help you:
Students & fresh graduates: If you are just starting, the complexity of the cellular industry can be a bit overwhelming. But don’t worry, I have created this FREE ebook so you can familiarise yourself with the basics like 3G, 4G etc. As a next step, check out the latest edition of the same ebook with more details on 4G & 5G networks with diagrams. You can then read Mobile Networks Made Easy, which explains the network nodes, e.g., BTS, MSC, GGSN etc.
Professionals: If you are an experienced professional but new to mobile communications, it may seem hard to compete with someone who has a decade of experience in the cellular industry. But not everyone who works in this industry is always up to date on the bigger picture and the challenges considering how quickly the industry evolves. The bigger picture comes from experience, which is why I’ve carefully put together a few slides to get you started in no time. So if you work in sales, marketing, product, project or any other area of business where you need a high-level view, Introduction to Mobile Communications can give you a quick start. Also, here are some templates to help you prepare your own slides on the product overview and product roadmap.