Dual-SIM smartphones let you use two SIM cards in a single phone. Most people who use dual-SIM phones find the functionality useful for mixing work and pleasure, rather than carrying separate phones for their work and personal contracts.
Dual-SIM phones are also useful for maintaining two personal contracts, whereby one might offer a good rate on calls and texts and the other offers unlimited data. Or perhaps you frequently travel abroad and would like to carry a UK SIM for when you're at home and another that is local to the country you're visiting.
Dual-SIM phones are incredibly popular outside the UK, but for some reason, us Brits have been left out of the dual-SIM party. This is one reason why the Chinese market has become a popular solution for picking up a dual-SIM phone.
Do bear in mind that many smartphones officially sold in the UK are single-SIM variants, whereas alternative models of that very same phone sold elsewhere in the world are dual-SIM. If you have a specific phone in mind, a good place to check is Amazon for any dual-SIM variants of that phone.
Xiaomi Mi 11 - Best Overall
The Mi 11 is a fantastic bit of hardware for the price. The fastest chipset around, a beautiful display, and strong cameras are all packaged within a lovely bit of industrial design.
Some will miss the IP rating, though for me the bigger downsides are the choice of a macro over a telephoto lens, the only average battery life, and a software experience that still lags behind the key rivals.
This phone went on sale in the UK on 22 March - see where to buy Mi 11.
Read our full Xiaomi Mi 11 review
Oppo Find X3 Pro - Best Display
The Oppo Find X3 Pro is a phenomenal phone by any measure. The 6.7in 10-bit 120Hz QHD+ panel is one of the best displays in any phone right now and Oppo backs it up with 65W wired and 30W wireless charging, a 4500mAh battery, and a top-tier camera that boasts 50Mp sensors on both the main and ultrawide lenses.
You’ll have to live without a periscopic zoom lens - the telephoto here is a measly 2x zoom - but Oppo instead includes a novel microlens camera capable of microscopic super-closeups. That's not the only oddity, as the design itself is utterly unique thanks to a seamlessly sloped camera module built right into the glass of the phone's body.
For pure performance the Find X3 Pro is also hard to beat, with all of the above plus a Snapdragon 888 chip, 512GB storage and 12GB RAM. You just have to be willing to pay the price, as it doesn't come cheap.
Read our full Oppo Find X3 Pro review
OnePlus 8 Pro - Feature-packed
The OnePlus 8 Pro is arguably the company's first full flagship, finally incorporating long-requested features like wireless charging and an IP68 waterproof rating to make it a genuine contender with Samsung's top flagships.
Understandably, the price initially went up accordingly, but it still represents serious value by flagship standards, and you will save at least some money by opting for OnePlus over most other manufacturers. (Since the release of its successor, its price has thankfully dropped).
The 8 Pro camera is OnePlus' best yet, and while it still lags behind rivals slightly in software the hardware is among the best around, which has helped to close the gap considerably. Throw in 5G, a great design, and the best Android skin around and the OnePlus 8 Pro is easy to recommend to anyone who can afford it.
Read our full OnePlus 8 Pro review
OnePlus Nord - Best Mid-range Phone
The OnePlus Nord is the best mid-range phone in the world right now. It looks and feels like a phone twice its price, with a display and main camera lens to match.
The 765G processor more than holds its own, and all of the camera lenses are solid except the forgettable macro shooter.
More importantly, you won’t find better at this price, or a better selection of the priority features for most users on a budget, with luxuries like wireless charging or an OTT 120Hz refresh rate ditched in favour of a focus on the fundamentals.
The Nord would be a good buy at £100 more - at this price, it’s a steal.
Read our full OnePlus Nord review
OnePlus 8T - Best Value Flagship
Ignore the price and the OnePlus 8T doesn’t feel like a desperately exciting upgrade from the 8 in some respects. But once you realise the price has dropped the phone begins to look much more compelling.
120Hz and 65W charging are welcome upgrades, even if they’re the sort of techie features that most users likely won’t care about too much. The software changes brought about by Android 11 are also almost all welcome, not least the always-on display.
From a hardware perspective the camera is the only real stumbling block, made worse by the decision to include the same main lens in the OnePlus Nord. And that’s really the main challenge facing the 8T: it’s good, but pound-for-pound the Nord is still better, leaving OnePlus hoist by its own petard.
Read our full OnePlus 8T review
Xiaomi Mi 10T Pro - Best Premium Mid-ranger
This Chinese phone is now one of our top recommendations in Xiaomi's line, if not quite up there with Mi 10 and Mi 10 Pro. We'd love to see an OLED panel, wireless charging and some refinements to the design, but these are all sacrifices we are prepared to make for what appears to be a very strong overall package that comes at a lower cost.
Xiaomi majors on value with Mi 10T Pro, carefully balancing cost-cutting with awe-inspiring. The powerful Snapdragon 865 processor, the 144Hz display, the 108MP camera, the incredible battery power and the 5G connectivity: these are all specs that have no business in the mid-range.
The on-paper specs of Mi 10T Pro are simply unbeatable among its peers.
Read our full Xiaomi Mi 10T Pro review
Xiaomi Redmi Note 10 Pro - Best Value Overall
The Redmi Note 10 Pro is essentially an upgraded Poco X3 NFC with a nicer display and better camera.
The 6.67in 120Hz panel boasts AMOLED tech, meaning superb contrast and vibrant colours. The 108Mp lead camera, meanwhile, excels and comes accompanied by a pair of secondary snappers that exceed expectation.
Fun extras like 33W fast charging, a headphone jack and even an IR blaster elevate the Redmi Note 10 Pro from good to great budget offering, considering what Xiaomi's incorporated here.
Read our full Xiaomi Redmi Note 10 Pro review
Xiaomi Poco X3 Pro - Best Budget Phone
The Poco X3 Pro isn’t perfect. The big battery makes it bulky, the cameras could be better and MIUI 12 leaves much to be desired, but they don't stop this phone from being an outrageously good budget offering.
In contrast, the phone boasts a myriad of strengths; strong specs leading to exceptional performance, a beautiful display and absolutely fantastic battery life.
The fact that you can get all of that for as little as Xiaomi is asking is almost unbelievable and like the Poco X3 NFC last year, the X3 Pro is on track to serve as the best budget phone of 2021.
Read our full Xiaomi Poco X3 Pro review
Xiaomi Redmi Note 9S - Best Battery Life
The Redmi Note 9S is one of the best budget phones we've seen. This is a fantastic phone for less than £200, a real all-rounder with decent performance and cameras, as well as mind-blowing battery life. The Redmi recorded the longest time in the Geekbench 4 battery life test that we've seen to date.
We are not fans of the rear camera module, and the lack of NFC in some territories is a shame, but those niggles aside it ticks all our boxes at this price point.
A fine example of not a lot of money very well spent.
Read our full Xiaomi Redmi Note 9S review
Nubia Red Magic 5S - Best Gaming Phone
The Red Magic 5G was undeniably one of the best gaming phones on the market, and this upgrade to it is almost identical but makes a few tweaks and removes some of our frustrations with the in-display fingerprint sensor. Its 144Hz display and stereo speakers are among the best in their class.
The phone is targeted squarely at mobile gamers and as such, some aspects are less well suited to mainstream users. All things considered, however, the Red Magic 5S offers everything budding gamers are looking for, not to mention 5G speeds, at a price that means it's hard to resist.
Read our full Nubia Red Magic 5S review
Your buying guide to the best dual-SIM phones in 2021
How do dual-SIM phones work?
Something we've noticed when shopping for dual-SIM phones is that the manufacturer very rarely provides any information about the functionality other than it exists. It doesn't tell you how the dual-SIM functionality works in practice, nor whether both SIMs support 4G/5G, or even what size SIM cards they accept.
You can never assume; you'll need to contact the manufacturer or check spec tables, reviews or forums to find out this information.
In all the dual-SIM phones we've tested, both SIMs are on standby at all times (known as dual-standby phones), but you can actively use only one SIM at a time. This means that either SIM can accept a phone call or text at any time, without you having to actively swap between them or reboot the phone.
However, if you get a call on one number while a call is active on the other, it won't start ringing in your ear or give you the option to put the first caller on hold - the call will simply not be successful.
What is the difference between Dual-Standby and Dual-Active?
Dual-active SIM phones use two modems and allow you to receive calls on both numbers at once.
If it's you who wants to make a call or send a text, Android has a standard SIM Management menu that lets you specify which SIM should be used for voice calls, video calls, messages and mobile data. You can either specify a particular SIM for each of these tasks, or leave the setting as 'Always Ask'.
The data connection is where there seems to be a lot of confusion when it comes to dual-SIM phones. Whereas both SIM slots on some dual-SIM phones are capable of supporting 4G or 5G connections, you can use data connectivity on only one SIM at a time.
Unlike with calls and texts, typically speaking the data connection can't be on standby for both SIMs; you must specify which SIM you want to use rather than select one when prompted - though some phones will let you set them to switch to the other SIM when the first can't make a connection.
By default, when you are using the data connection on one SIM and a phone call comes in to the other, it will pause the data connection on the first.