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So, what is a dual SIM phone?
In essence, it’s exactly what the name suggests: a phone that can use two different SIMs. A SIM, or Subscriber Identity Module, is (typically) a small, removable plastic card with metal contacts that fits into a slot in the side of the phone and helps identify a device on a cellular network. If the SIM is authorized to connect to the network, you’ll get service. If it isn’t, you won’t.
Most phones sold in the United States only have a single SIM slot. Dual SIM phones are far more common elsewhere in the world, however, and many manufacturers offer different versions of their phones because of this.
Technically, things don’t end with just two SIMs. Triple or even quadruple SIM phones do exist, but they’re very rare, and typically only available in developing markets like India. They offer little extra for the vast majority of travelers, and there’s no particular reason to try to hunt one down.
Why Use a Dual SIM Phone?
People tend to use dual SIM phones for two main reasons in daily life. In countries where calls and texts are typically free between devices on the same network, customers often have SIM cards from two different companies and switch between them depending on who they’re calling.
Likewise, people who don’t want to carry a separate phone for work and personal use will often end up with a dual SIM model that lets them combine both numbers in a single device.
There’s some impact on battery life when using two SIMs, but it’s fairly minimal.
How Is a Dual SIM Phone Useful for Travel?
Dual SIM phones are very useful for international travelers, since they can provide the best of both worlds when it comes to staying connected.
You can buy and use a prepaid SIM card from whatever country you’re traveling in to get cheap local calls, texts, and data, while still keeping your usual number accessible. Equally, you can drop an international SIM card into one of the slots, and retain your home SIM in the other.
Almost all dual SIM phones let you set a default SIM for calls, texts, and data. You can often also turn data roaming on or off individually, and disable one or both SIMs as needed.
This approach gets around a problem faced by many international travelers: how to avoid paying high roaming fees to use your phone abroad, while still being contactable by family, friends, and institutions like banks that want to send authentication codes to your usual number.
As long as you have roaming enabled with your home SIM, you’ll still receive calls and texts to it, even with the other SIM set as the default.
Not All Dual SIM Phones Are the Same
Just because two phones have dual SIM capability doesn’t mean they both work exactly the same way. There are a few technical differences to be aware of.
Dual Active vs Dual Standby
In the past, one of the biggest differences between dual SIM devices was whether they were dual standby (DSDS) or dual active (DSDA). As the names suggest, dual-active devices can both be active on a call or using data at the same time. Dual-standby devices will “listen” with both SIMs, but only one can be active at once.
This mattered far more with older GSM voice and data networks, since using one SIM for calls, texts, or 2G data would prevent the other from receiving a call. LTE networks don’t have the same limitations, and most phone makers now don’t bother with the extra hardware required for dual-active support.
These days, the main thing you need to remember with DSDS devices is that unless your carrier is using VoLTE (Voice over LTE), the other number will go to voicemail whenever you’re on a call,
What About eSIMs?
Embedded SIMs (eSIMs) have been available in a few Android devices for the last two or three years, but it was Apple adding it to the latest iPhones that really popularised the technology.
Rather than using a physical, removable SIM card, eSIMs are built into the phone and configured via software. Since only a small number of carriers currently support the technology, phones with eSIM also include a separate physical SIM slot as well.
As a result, the iPhone XS and iPhone XR models are the first dual SIM iPhones that Apple has made. In most of the world, these models have one physical SIM slot, coupled with an eSIM. Most or all of the versions sold in Hong Kong, Macau, and China, however, take two physical SIMs instead.
While using an eSIM to provide a second SIM option is certainly useful, it doesn’t yet provide the same flexibility as two physical slots. As mentioned, carriers around the world have been slow to support eSIM, with none other than a few international SIM providers currently offering prepaid service.
We’ve talked a lot more in the past about eSIMs for travel, and the best way to use them.
Don’t Forget About MicroSD Cards
Many dual SIM Android phones also include microSD card support, letting you add additional storage space as needed. If that’s something you intend to use, it’s worth checking the details of exactly how it’s done on the device you’re buying.
Some dual SIM phones have a separate microSD slot, so adding extra storage won’t affect your ability to use a pair of SIM cards.
Other models, however, save money and space by combining the microSD card reader with one of the SIM card slots. In that case, you can use either two nano SIMs, or one SIM and one microSD card, but not all three cards at once.
What’s the Best Dual SIM Phone?
The best dual SIM phone, for travel or any other purpose, is likely to depend as much on where in the world you’re buying it as anything else. As mentioned earlier, relatively few phones sold in the United States have two physical SIM slots. You’ve got a few more options if you’re happy to use an eSIM, but it’s still a limited range.
Elsewhere in the world, it’s a different story. Not only are there far more dual SIM phones that aren’t even sold in the US, as mentioned earlier there are international variants of several popular models that have two SIM slots instead of one.
It’s often possible to buy these international models from the US Amazon store and elsewhere, but they typically don’t include a manufacturer warranty. If they fail after the return period (typically 30 days), you’re on your own.
Best Dual SIM Phones With Two Physical SIM Slots
OnePlus is one of the few companies selling high-end smartphones with two physical SIM slots in the US (and elsewhere), and is an obvious recommendation here. We’ve reviewed the OnePlus 6 and 6T in the past, and the OnePlus 7 and 7 Pro continue where they left off.
If you’re buying outside the United States, or are happy with the lack of warranty support when buying from a US vendor, the international version of the Motorola Moto G7 is our top budget pick.
Best Dual SIM Phones With eSIM
Once you start including phones that have a physical SIM slot and an eSIM, your options open up a little more. Apple’s latest models both fall into this category, so if you’re an iPhone fan and have the money to spend, both the iPhone XR and XS are good dual SIM choices.
The best dual SIM phone that uses an eSIM right now, however, has to be the Google Pixel 3a. It’s remarkable value given the high-end camera, regular software updates, headphone jack, and more, and we’d still buy it even if it only had a single SIM. With two, it’s a no-brainer.
What Other Dual SIM Devices Are There?
While multiple SIM slots are most often seen in smartphones, that’s not the only place you’ll find them. A few companies have come out with dual SIM mobile hotspots, and it’s still possible to find Android and iPhone dual SIM adapters if you look hard enough.
Dual SIM Mobile Hotspots
While the vast majority of portable hotspots have a single SIM slot, there are a few that buck the trend. The GlocalMe G3, one of our top mobile hotspot picks, actually has three SIMs: a pair of slots to put physical SIM cards in, along with an eSIM that provides surprisingly affordable roaming data packages.
The advantage of that approach in particular is being able to use the roaming data as soon as you arrive in a new country, switching to a local SIM whenever you get around to buying one. Only one SIM, physical or embedded, can be active at once, but that’s not an issue with data-only devices like these.
Hotspots like these are only a partial communication solution, since you’re still restricted to the SIM card in your phone for calls and texts. Given the focus on data for most travelers, however, that limitation often doesn’t matter much at all.
Dual SIM Adapters
A few years ago, dual SIM adapters were quite common for both Apple and Android devices. They come in two main types: a ribbon cable that hangs out of the phone’s SIM tray, and a Bluetooth adapter with a pair of SIM slots.
For a long time adapters like these were really the only way of getting a dual SIM iPhone in particular, but both types have their flaws. The ribbon cable approach is ugly, cumbersome, and quite delicate. The Bluetooth adapters are typically quite expensive, don’t have great battery life, and mean carrying a second device.
Unless you need calls and texts on both SIM cards, you’ll usually find an unlocked portable hotspot is a better choice than any of the dual SIM adapters. That probably helps explain why the adapters have dropped in popularity in recent years.
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Dual SIM phones come in many different variations. They’re easily available in some parts of the world, and hard to find in others. Some let you use two physical SIM cards, while others use an embedded SIM that’s poorly supported by most carriers. Using a second SIM will stop you adding extra storage with some dual SIM phones, but not others.
Whatever type you go for, however, you’ll find a dual SIM phone useful overseas. Being able to drop in a prepaid SIM to get cheap local calls, texts, and data while still having access to your home number is valuable on the road. You’ll save money and time, with no extra effort.
If you’ve got the option where you live, it’s well worth making your next phone a dual SIM model.
Got any questions about dual SIM phones? Drop them in the comments!