The difference between SIM and eSIM (and what the future holds)

Pretty much ever since modern smartphones have been available to us, we've been dealing with the small piece of plastic inside known as a subscriber identification module (SIM). When you get a new phone, your service provider likely pops in a SIM and you go on your way, or you switch it over yourself from your old device. While SIM cards are a big part of an enormous mobile market, there's a new type of technology causing a bit of a disruption. You'll be hearing more about embedded SIM (eSIM) as it becomes more common, but what's the difference?

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The difference between SIM and eSIM

If you're carrying around a phone that has network access, you can probably also see your provider's name in a top corner. This is all brought to you by the SIM card inside, which identifies your phone and what type of plan it's using based on a profile. Traditional SIM cards can only be linked up with one profile and are generally useless if that profile stops being used.

Phones are not the only devices using SIM cards, and we've seen plenty of laptops and tablets take advantage of the tech for years, especially in the enterprise sector. Lenovo's ThinkPad lineup of business laptops is a great example.

SIM cards come in a few different sizes, evolving as phones have been slimmed down and packed with other hardware. You have Standard SIM that's about the size of an SD card, Micro SIM that's slightly smaller (15mm x 12mm), and finally Nano SIM (12.3mm x 8.8mm) that is the smallest of them all.

Standard, Micro, and Nano (left to right)

Image courtesy of Wikipedia.

An eSIM, however, isn't a removable card. Instead, it's embedded (that's the 'e') on the device's motherboard or part of the processor — there's nothing to insert and nothing to remove. Because an eSIM cannot be removed if you'd like to switch providers, remote provisioning is used instead. Instead of going to a store, acquiring a new SIM card, and swapping it out, with an eSIM the changeover is handled entirely virtually.

eSIM has the ability to use and store multiple profiles. If you travel, for example, getting access to a new country's mobile provider won't require tracking down and swapping out SIM cards. You also won't have to worry about cutting a Micro SIM down to fit the Nano SIM slot on your phone (which is seriously not fun). eSIM also takes up far less physical room inside a device, which is much more important in wearables but also becomes a factor as phones, tablets, and laptops get thinner.

What does the future of eSIM look like?

The Apple Watch 3, Google Pixel 2, and Microsoft Surface Pro LTE are a few high-profile devices that feature eSIM technology right now, and the new Always Connected PCs from Microsoft's partners are adding to the list.

It's clear that the need for eSIM is growing, and its flexibility is no doubt attractive to a large audience. As Executive Editor Daniel Rubino wrote in his feature on eSIM, "The ability to take a PC or 2-in-1 wherever in the world you are and still have multiple ways to get on the internet is going to be critical for businesses, the modern nomadic millennial workforce, creators, those who are self-employed, and even regular consumers."

Still, it must continue to be accepted, served, and utilized by more mobile carriers and device manufacturers. For example, the eSIM inside the Surface Pro LTE is currently sitting dormant (there's also a traditional SIM slot), but that will soon change. Microsoft is expected to start selling chunks of data rather than full plans, letting anyone with an eSIM device pick up a few gigabytes here and there when necessary.

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As eSIM becomes standardized by the GSMA and more people get turned onto the benefits, it's hard to imagine we'll still be dealing with the plastic traditional SIM cards in the future. When you can visit, say, the Microsoft Store and browse and pick out a data plan just like you're buying an app or movie, it will be hard to think about ever going back to the way it was.

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Cale Hunt
Senior Editor, Laptop Reviews

Cale Hunt is formerly a Senior Editor at Windows Central. He focuses mainly on laptop reviews, news, and accessory coverage. He's been reviewing laptops and accessories full-time since 2016, with hundreds of reviews published for Windows Central. He is an avid PC gamer and multi-platform user, and spends most of his time either tinkering with or writing about tech.

  • Thanks for the info !
  • Once esim has wide support amongst many providers it'll be grand. Whilst in many places the choice is currently so anaemic as to be no choice at all, every device released must be able to handle both trad. sims and esims or the customer will be at the mercy of the one provider available to them who can then charge whatever they wish. This is why I really hope MS does not limit the not-Phone devices to esim only, or i.e. UK users will be paying through the nose for data with the one provider signed up to offer esims to MS devices as currently stated by MS.
  • My biggest fear for eSIM is that the carriers will some how get in the way of it working the way we all see it working. I can imaging them trying to force ESIM the way of regular Sims. Don't know why I see this. Lol maybe because of how they continue to set the US back in the States. I see ESIM working better in the EU to be honest. I just don't trust AT&T and Verizon. I can somehow see T-Mobile doing right by ESIM through. Any thoughts
  • Yeah my worry is the carriers getting in the way too
  • I am with you these devices need to have both, so we aren't handcuffed!
  • Thanks a lot. I always thought it's like this but never knew it. Especially the part about the multiple profiles is great. I always use a Dual Sim phone for this. Didn't knew that eSIM is perfect for me.
  • I bet you can switch / toggle 1 profile between NB & mobile too.
    And you can tether from your NB (esp with those long lasting ARM) when you sit.
  • No never. The is why I use Sim and not cdma. I like that in can switch by moving Sim. This new thing makes it so it is no different then cdma and will be harder to change phones when you want to. All these good things you say will be restricted like Verizon and sprint do already. They can say your can't use a phone because it is not on a list to.
  • Interesting perspective. Where is your source for that theory?
  • Verizon refusing to authenticate the Nokia 950 would be one example.
  • I have never had an issue dropping a Verizon SIM into any phone post-Lumia 950. Surface Pro, OnePlus, Razer Phone, various iPhones, all worked.
  • My understanding was that Lumia (not Nokia) 950/XL did not support CDMA, either by lack of the radios, or intentional restriction. The alternative is GSM, not SIM, BTW. Verizon could not authenticate those phones, unless a new CDMA compatible version were made. Same with Sprint. GSM and CDMA are mobile technologies. the SIM is a physical provising technology. Notice Daniel used a Verizon SIM. The key is that the device supports the mobile technology (think radios), and the provider will authenticate the device. As it has always been the case, SIM or otherwise, a carrier/device provider has incentive to keep you from moving to a new provider. They also have an incentive to lowering the friction to coming to them. AT&T wants it easy to adopt AT&T, and hard to leave them, as do all of them. eSIM can make both easier.
  • Profiles will be sold in MS store...
  • Or maybe they will say you can only provision an eSim or switch devices once a month. Carriers will find some way to abuse it if they can make more money.
  • "This new thing makes it so it is no different then cdma and will be harder to change phones when you want to."
    This is literally the opposite of IMEI on CDMA. Not even close. I suggest digging deeper on this topic.
  • How is this different from what Verizon does (or did)? At least in the old days they didn't have sim cards. Am I remembering that right?
  • Well, it's very different. Each CDMA phone had a hardcoded IMEI number like a SSN for the phone - you get one and only one. That number had to be in their DB for the phone to be activated. If that IMEI number was not in their DB, well, phone no worky. eSIM is not like that at all. eSIM is programmged on the fly, so it's like a variable IMEI number, not one "locked" to a carrier. eSIM is just SIM. It works anywhere where SIM works, it's just virtual instead of physical now. eSIM and IMEI is the total opposite.
  • Sorry, I decided to have a beer with lunch, maybe I'm not fully following. You're not saying that IMEI will be disappearing? That number is how the carriers shut down stolen phones & such.
  • No, that's not true. IMEI and eSIM are not independent and distinct. IMEI is a hardware identification, like a MAC address on a network device. The IMEI, or something like it, will still identify the device. The eSIM will identify the user parameters identified/associate with, the use of the device, like phone number, carrier, plan, etc. The IMEI is generally hardcoded into the device, like a MAC address, but both are potentially spoofable. You aren't going to be dynamically changing the device ID. You will be dynamically changing what that device is authorized to do, and on what network.
  • It looks perfect for future handheld game consoles, e.g., Switch, or if there's handheld Windows gaming device. You could play AAA online whenever and wherever you want with less restriction.
  • Why not coming with a converter card that transforms your current phone to eSIM specifications?
  • Interestingly enough, the new HP Envy x2 (Qualcomm), or at least the test version that Thurrott is testing, didn't come with an eSim according to his initial evaluation. I definitely believe eSim is the only way to go in the near future. "That nano-SIM slot is interesting: My understanding was that meeting the requirements of Microsoft’s Always Connected PC initiative meant that the device would have an internal E-SIM. But the HP does not. I’ve outfitted it with a Project Fi data SIM, which works just fine"
  • Maybe there's more than one version
  • eSIM doesn't preclude a SIM slot and the ability to use it. My iPhone X supports eSIM though AT&T stuck a physical SIM into it. I am financing my phone (at 0% interest) so currently I couldn't make use of either some other carrier's SIM or the eSIM option. That's fair. At some point though, I could have it reprovisioned electronically via eSIM, or stick a different physical SIM in the slot, if I needed to use a carrier that didn't yet support electronic provisioning. Do keep in mind you need some sort of connectivity to do that electronic provisioning. WiFi would be the most usual. If you aren't paying for, and connected to AT&T for data, Verizon couldn't provision your eSIM over that non-existent data link. This is more important when you get to that foreign country and no longer can connect to your service provider. Getting local access is going to rely on some connectivity. You will need to plan ahead.
  • Very informative article thanks, what might be the security/privacy risks with a sim you cannot remove or turn off if it`s "always connected"?
  • The day the phones switch to these e-sims is the day I stop upgrading my phones. Why would I wnt the repair shop to have full access to my service provider and all the related data? Why would I risk someone cloning my phone and access my bank accounts? Not going to happen. Not with me at least. If I am traveling and wish to use a local sim it is no biggie to carry a second phone. I do it all the time. It is already a problem in the US. 90% of the sims won't work on foreign phones. Foreign sims won't work on US phones!
  • Beyond eSIM, there's already something called iSIM, developed by ARM.
    Far smaller than an eSIM and can be integrated into the SoC itself.
  • What would that Mean for dual-sim? I always pick phones that have this ability. One sim for work and one private. Does esim include dual-sim or would you need the technology to be twice in the phone?
  • That's a good question. eSIM is really more electronic, than embedded. The latter makes it sound like there is a physical little tiny SIM permanently glued in. It is more data areas set aside to hold the information normally held in the physical SIM. Nothing would preclude there being more than one such data section. Could even allow for more locations, without the space that would require with current traditional SIMs. Could easily provide a work, personal, and travel eSIM option. The industry just needs to work out the standards for how this would work, and the SOC guys build it in.
  • Thanks for the reply. And what would that mean for the antenna? Could esim use 1 antenna for multiple connections? Because if I'm not mistaken a dual-sim phone also needs 2antennas ?
  • My understanding is, eSIM technology has existed for several years, and was actually developed and/or pushed by Apple for their iPhones, but the previous efforts to standardize and adopt the tech by phone/electronic manufacturers/Industry was derailed by, I think, the phone companies who wanted to keep their "monopoly" on sims/locked phones. Obviously, things have had major changes over the last several years, and that's a good thing. I would say eSIM technology, combined with the USB-C Standard Port/USB-Power are two of the biggest positive changes for cell phones in recent years.