Xiaomi Mi Mix 3 full review

Xiaomi's flagship slider phone, the Mi Mix 3, officially retails in the UK at £499 via the Mi Store. We recently saw a newer model announced in China, but for now the Mi Mix Alpha is unobtainable (and very, very expensive).

The standard version is now joined by a 5G variant, available through Vodafone, O2 and Three, or SIM-free from Amazon (find out whether it's worth upgrading to 5G now in our head-to-head comparison).

It's all about the cameras and the display in the Mi Mix 3, which refines the already great Mi Mix 2S on two primary fronts. This new generation also includes a dedicated button for calling up either the Google Assistant or Mi AI client, depending on whether you buy the UK or Chinese model. 

Interestingly, Mi Mix 3 line lacks an in-display fingerprint sensor (instead found at the rear), which is one of the hottest new trends of this year, and something of a surprise for a phone that began life as Xiaomi's 'concept' phone, stealing column inches for its revolutionary design.

Whether its absence is evidence of a cost-cutting decision or the fact that implementing two new kinds of screen tech at once is tricky we're not entirely sure, but Mi Mix (and now Mi 9 also) is alone in the Xiaomi phone family in its offering of wireless charging, and the Mix 3 is the first in the entire line-up with a magnetic sliding screen. Xiaomi has since experimented with achieving the full-screen display using a pop-up selfie camera in the Mi 9T and Mi 9T Pro.

Also see: Best Xiaomi Deals and Mi Mix Fold price, release date and more.

Mi Mix 3

The design remains something special, once again a creation of Phillipe Starck, but the slider concept is not entirely new, having already been seen in the Honor Magic 2 and Lenovo Z5 Pro - but in those phones it really doesn't achieve much, aside from moving the selfie cameras out the way to allow an uninterrupted full-screen view.

With Mi Mix 3 you slide to start: it can automatically launch the selfie camera, or provide a bunch of quick-access functions such as a timer, recorder, calculator, notes app, camera and the weather. On the Chinese model there are mobile payment options here too, though they are Chinese only so unsurprisingly they are gone in the UK version.

For this review we tested both the Chinese ROM version of the Mi Mix 3, and the UK model that went on sale here on 16 January. As we outline below you can save some money opting for the Chinese version, but as well as putting up with the preinstalled Chinese apps, Chinese Mi AI client and Chinese mobile payment services, you'll need to install Google services on the Chinese model (here's how).

Mi Mix 3

Also see: Best Xiaomi phones.

Mi Mix 3 Design & Build

The Mi Mix was the first phone to introduce the 'full-screen display', though in truth it never has been entirely bezel-less. The original model was all screen on three edges, but with a chunky chin at the bottom where you found the upside-down selfie camera. And gosh was that annoying.

Over the years the design has been refined, with this chin getting slimmer with each new generation, but only now in the Mi Mix 3 has the chin been removed altogether.

It's worth pointing out that there is still a tiny but very much present screen bezel running the entire circumference of the phone, but Mi Mix 3 achieves an astonishing screen-to-body ratio of 93.4%. Though a 100% screen-to-body ratio would look phenomenal, we would worry about its fragility.

Xiaomi has achieved this by implementing a sliding screen mechanism that uses neodymium magnets with a life expectancy of 300,000 cycles. Most smartphones are sold on two year contracts, so using this as the benchmark you could slide open the screen 410 times a day without worrying about it breaking. That said, without extensive use it's difficult to know how much dust and grime will find its way under the display.

Mi Mix 3

There's also an Always-on Display option, showing the time, date and notifications, which should reduce the number of times you feel the need to wake the screen. And the speaker is actually built into the top bezel (though you'll need to squint to see it), which means you don't need to slide down the screen to hear your recipient at the other end as you do with the Honor Magic 2 and Lenovo Z5 Pro (though you can use it to answer a call).

The sliding action feels smooth, with the screen maintaining the same distance from the chassis and offering a satisfying click as it opens and closes. You can also choose from five different sounds that play as you slide open or shut the screen - Hi-tech, Warrior (our favourite), Mechanics, Intellect and Lighter - plus a few more available to download.

On the Lenovo and Honor alternatives the sliding screen is of little use other than hiding away the selfie camera(s) and other blemishes that would usually adorn the front panel of a phone. But on the Xiaomi, sliding open the screen can actually launch the front camera, or if you're not a selfie fiend you can set it to offer other quick-access options such as the weather, a note-taking app, a timer, a voice recorder, the camera, torch, a QR code scanner or a calculator (mobile payments, too, if you've bought the Chinese version). Though it's not immediately obvious how you might go about accessing the home screen from here, touching any blank area of the screen achieves this.

Whereas it might feel a little like a gimmick on those other phones, here the sliding screen not only adds functionality but allows for a big improvement on existing functionality. If you've ever used a Mi Mix phone before then you'll know that putting the selfie camera below the screen just does not work: the angles at which you need to hold the phone in order to capture a selfie where you look anything other than deranged are difficult to achieve, and the filters in apps such as Snapchat just don't play well with the format.

Now the selfie camera is not only in the correct position, but it's better than ever - up from a single-lens 5Mp camera to a dual-lens 24Mp + 2Mp model, with the second lens used to blur the background on portrait shots, plus there's an LED flash. The quality is significantly better, and the software integrates Xiaomi's AI, able to intelligently select the scene.

Mi Mix 3

Removing the camera from the chin of the phone also means you no longer need the chin, so Xiaomi has reduced the bezels and increased the size of the screen - from 5.99in to 6.39in. Given that it has a larger screen and a new sliding screen mechanism it's incredible that the Mi Mix 3 is fractionally shorter and narrower than the Mi Mix 2S, and only 0.4mm thicker. The battery capacity has been reduced by 200mAh, of course. This all helps toward making it feel more comfortable to use in a single hand, too.

The display itself has a taller aspect ratio than previously, now at 19.5:9 (previously 18:9). There's no notch, like you see on the Mi 8 family, so it's pretty much pure screen.

Thankfully it's a nice screen, and this is an AMOLED panel which is our favourite kind of screen tech, bursting with vibrant, punchy colours and offering brilliant whites and deep blacks. It supports Xiaomi's Sunlight Display and Reading Mode, and indeed is easily bright enough for use in direct sunlight - we measured 407cd/m2 in our tests, which falls a little short of Xiaomi's claimed 600cd/m2 but is still very good.

The resolution is Full-HD+, which might sound less impressive than on other flagships. It's true that there is a visible difference with Quad-HD and Ultra-HD, but these things cost money and eat the battery - Samsung is now offering Quad-HD as an option but defaulting to Full-HD in its flagships, for example. Xiaomi has never added anything higher than Full-HD to any of its phones, and we're not sure it ever will - this resolution is perfectly adequate for clear text and images, and for enjoying games and media (graphics run faster at lower resolutions in any case). 

Elsewhere the design of the Mi Mix 3 is as appealing as ever, with its glossy black, tough ceramic coat and carefully crafted workmanship seen throughout. It is now lacking the 18K gold camera and fingerprint sensor surround, but while it was a nice thing to show off it never really added anything other than a bit of bling.

The dual-camera and fingerprint scanner remain in the same positions at the rear, though we did notice more than previously how the camera's positioning causes the Mi Mix 3 to rock slightly when used on a desk or flat surface. And, as before, you'll find a volume rocker and power button on the right side, pin-operated SIM tray on the left, and a USB-C port at the bottom. There's no physical home button, but you can opt for full-screen gestures or onscreen home, back and multitasking options.

Mi Mix 3

It's still a downward-firing mono speaker - albeit a very good quality one, with minimal distortion at full volume - and there's still no headphone jack, and you won't find a USB-C to 3.5mm adaptor in the box. Instead you get a 10W wireless charger, which is incredible - we know of no other Qi-compatible smartphone that is actually bundled with the necessary charger.

New is an additional button on the phone's left side which calls up the Mi AI voice assistant on the Chinese version of the phone, and the Google Assistant on the UK Mi Mix 3. You can also change the function of this button to open the front or rear camera, turn on the torch, turn on Reading mode, or open Google Search or the previous app. Alternatively, you can turn it off completely.

In the next revision to the Mi Mix line we'd hope to see waterproofing and an in-display fingerprint sensor - though not if it means that attractive price will rocket. Don't hold out your hopes for a higher-resolution display.

Mi Mix 3

(Also see: Best Chinese phones.)

Mi Mix 3 Core Hardware & Performance

Inside the UK Mi Mix 3 is exactly the same hardware as you find in the Mi Mix 2S. 

This means you get the Qualcomm Snapdragon 845 running at 2.8GHz. It's an octa-core processor built on the second-generation 10nm manufacturing process, and integrates Adreno 630 graphics.

This chip is paired with 6GB of RAM and 128GB of internal storage. It is not expandable through microSD, but sufficiently generous that this shouldn't be a problem.

As before we are blown away by its performance, despite the fact it actually performed a little slower in our benchmarks than did the Mi Mix 2S. It's normal for synthetic benchmarks to fluctuate, though, and it's the real-world experience that matters more. It can handle anything and everything, all at once.

We've charted its performance results below along with the Honor Magic 2, Lenovo Z5 Pro and Mi Mix 2S. The Honor is fastest with its 7nm Kirin 980 chip, and the Lenovo Z5 Pro slowest with its mid-range Snapdragon 710 - though we have heard a Snapdragon 855 'Z5 Pro GT' version with 12GB of RAM is imminent.

In terms of connectivity there's everything here bar an IR blaster, which are increasingly rare but still found on some Xiaomi phones. There's support for 4G dual-SIM dual-standby, and complete coverage of UK 4G LTE network bands.

You also get dual-band 802.11ac Wi-Fi, Bluetooth 5.0 and GPS and GLONASS, and while on the Chinese version the slider screen payment options are all Chinese services even here there is support for NFC and Google Pay.

As we noted the battery has been reduced by 200mAh, but Mi Mix 3 still supports Quick Charge and wireless charging (now with a 10W Qi charger and 18W wired charger in the box). You'll easily get a day's life from the phone, and potentially more depending on your usage.

Mi Mix 3

Mi Mix 3 Cameras & Photography

We've already touched on the selfie camera, which has seen big changes in this new model, but the primary camera has some enhancements too.

As previously it's a 12Mp + 12Mp dual-lens camera, but some software improvements mean the quality is higher than ever. Whereas Mi Mix 2S scored 97 points in the DxO Mark test (and the Mi 8, which uses the same camera, 99 points), this Mi Mix 3 nets 108 points.

The setup comprises one Sony IMX363 wide-angle lens with f/1.8 aperture, 1.4um large pixels and Dual Pixel Autofocus, and one Samsung S5K3M3+ telephoto lens with f/2.4 aperture and 1.0um pixels. The combo boasts optical zoom and four-axis OIS, and is capable of 960fps slow-motion video.

It's an AI camera, which means it can intelligently select the correct preset scene for your photo, without you having to give it too much thought. It can also use the second lens for Portrait mode in which it achieves bokeh-effect background blurring. 

You can see some of our test shots below. The first is a simple point-and-shoot from our seventh-floor office terrace, looking over the St Pancras Renaissance Hotel the other side of Euston Road. With no input from us the image is true to life with realistic colours and great detail, well exposed and sharp right to the edges.

Mi Mix 3 Auto

With HDR mode engaged the shadows and highlights are enriched, but some evidence of blurring goes to show how important it is to hold still the camera during such shots, especially on a windy roof terrace. Even so it's still a very decent photograph that shows Mi Mix 3 is capable of great things.

Mi Mix 3 HDR

We were less enthused by its low-light shots, and also surprised since the Mi Mix 2S seemed to handle these much better. The camera struggled to light the scene without resorting to the flash, and much noise is present. Of course we have seen significantly worse.

Mi Mix 3 Low Light

Mi Mix 3 Software

The Mi Mix 3 runs MIUI 10, which is a customised version of Android 9.0 Pie. The major differences are found in the Settings menu, which is slightly reordered, in the drop-down notification bar and in the fact there is no app tray, so all app shortcuts are on the home screen. You an also change the theme, and you'll notice the default app icons look a little different to in standard Android.

If you've bought the Chinese version then note that they don't use Google services, so MIUI has its own apps for pretty much everything you'd ordinarily use Google's apps. You can use these, or you can install the apps with which you're familiar - but here is the catch: You'll need to install them yourself, unless you buy a UK or Global model.

A recent minor amendment to the procedure means you will need to have a SIM card in the phone before allowing it to install files from unknown sources, but we expect if you're setting up the Mi Mix 3 for personal use you will have installed a SIM in any case.

Mi Mix 3

Having used MIUI for many years we have found it quickly becomes familiar, and actually its extra features may make it preferable to standard Android. The likes of Dual Apps and Second Screen are worthy of high praise, particularly if you'll be taking advantage of the phone's dual-SIM functionality.

We're also keen on the backup options, which make it so much easier to get back to where you were following a factory reset, and you'll find features such as Split-Screen here too.

A new addition here is Taplus, which we've not seen before on a Xiaomi phone, and the description suggests you tap and hold an item to learn more. We tried it but couldn't get it to work, so it could be only for the apps we're not using. 

The oddly named 'App Vault' is swiped in from the left of the home screen, and as you see on many Android phones pulls together quick access to your most commonly used apps, notes and calendar events.

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Xiaomi Mi Mix 3: Specs

  • 6.39in Full-HD+ (1080x2340) AMOLED display
  • MIUI 10 (based on Android 9.0)
  • 2.8GHz Qualcomm Snapdragon 845 octa-core processor
  • 6GB/8GB RAM
  • 128GB/256GB storage, non-expandable
  • dual-SIM dual-standby (2x nano)
  • all UK 4G bands
  • 802.11a/b/g/n/ac Wi-Fi
  • Bluetooth 5.0
  • 24Mp + 2Mp selfie camera
  • 12Mp + 12Mp dual-lens rear AI camera
  • USB-C
  • 3,200mAh battery
  • wireless charging (10W Qi charger supplied)
  • 157.9x74.7x8.5mm
  • 218g