Vivo X21 review: includes innovation that rewrites the fate of future smartphones

Vivo X21 product shot 3

Rating: 7.7/10


  • Presence of an in-display fingerprint sensor
  • Even face unlock is super fast
  • Premium glass body
  • Decent performance 
  • Dual Engine Quick Charge is as good as Dash Charge


  • Surprisingly, front camera is meh
  • No USB Type-C port
  • Software handles the notch poorly
  • No wireless charging

Okay, truth bomb time: I honestly didn’t think Vivo would be the first smartphone brand  bring an innovation as important as the in-display fingerprint scanner to the world. This feat in itself deserves an applause. 

The company showcased this futuristic tech for the very first time at MWC Shanghai in mid-2017. And since then, retail smartphones like the Vivo X20 Plus UD and the Vivo X21 UD are the first to showcase the in-display (or under display) fingerprint scanner to the whole world. 

Now, the Vivo X21 – without the UD suffix – has officially launched in India and I am glad Mr. Phone got the opportunity to test it out before the launch.

So, let’s not waste any more time and get down to the full review of the phone.

Vivo X21 product shot 8

Vivo X21 in-display fingerprint sensors and display: a peek into the future

Let’s talk about the in-display fingerprint sensor first and how it actually works. Essentially, a sensor – just like your camera’s sensor – sits around 0.68mm below the AMOLED display of the phone. The moment you press the designated area to register your fingerprint, this sensor captures reflections of your fingerprints through the OLED pixels. 

Let me answer a few questions that might be on your mind:

  1. Who makes these in-glass fingerprint sensors?

    Synaptics, a company known for innovation in touch displays and biometrics, has a solution called the FS9500 ClearID. The Vivo X21 uses the help of ClearID sensor to register fingerprints directly from the display substrate.

    Synaptics sensor

  2. How fast does it take to unlock the phone?

    Let me put it this way; it is not as fast as your traditional physical fingerprint scanner like TouchID. It takes about 0.7 seconds to unlock the phone. But do remember, that we are talking about first generation technology. TouchID wasn’t blazing fast on the iPhone 5s when it launched first, was it?

  1. Can the entire display turn into a sensor?

    Absolutely. In fact, the Vivo Apex concept phone had an entire area in the bottom half of the display cordoned off exclusively for the fingerprint scanner. However, such a solution is bound to be expensive.

  2. Does it work underwater?

    Oh yes, it does. Unfortunately though, the Vivo X21 is not waterproof. But, it did work with wet fingers during my testing.

    Vivo X21 product shot 1

  1. What’s the point of using an under-display fingerprint sensor?

    Firstly, with the in-display fingerprint scanner, smartphone engineers can finally dream of a fully bezel-less phone. Furthermore, in the future, the entire display can turn into a fingerprint reader and therefore eliminate the need to locate the scanner. 

  2. Does it work with a screen guard on?

    Surprisingly, yes. In fact, the X21 comes with a pre-applied screen guard and I could use the sensor regardless.

  3. Can I use it to securely lock other apps?

    Yup. No problemo.

Coming to the most important point: how was my experience of using the in-display fingerprint scanner? Well, setting it up takes longer than physical sensors. But, that’s okay. I am not going to complaining. Here’s the thing though; when the setup process asks you to hold the edges of the finger to register your prints, ensure that you try different angles. Also, it is really vital that you keep the fingers clean during the detection process. Follow these steps diligently, and the scanner will have a much lower fail rate. I learnt it the hard way. 

Moreover, you really need to press deeply for the sensor to identify your prints. Thankfully, the phone vibrates if the fingerprint is not registered, and therefore you don’t have to second guess. Yes, it is a small learning curve but I am going to cut some slack because it is first generation tech. Also, you have three different types of fingerprint unlock animations that you can choose from. These animations look like they were inspired a lot by the Matrix.

Vivo X21 product shot 7

If you do struggle with the in-display fingerprint sensor, you can opt for the Face Unlock instead. And, Vivo uses an infrared-based sensor for unlocking the phone. This is cool because it unlocks really fast – almost as fast as the OnePlus 6 – and it feels secure too.

Moving on, at the moment, in-display fingerprint scanners play nicely only with AMOLED tech and I am really not complaining. Because, this 6.28-inch 19:9 aspect ratio panel with a resolution of 2280x1080p is bright, colourful, and crisp for most scenarios. In fact, the blacks are so deep that the Always On display looks as impressive as Samsung’s flagship Galaxy S9. Don’t get me wrong though, Samsung’s displays are still the best in the business. No beating that. 

With an AMOLED display you will also have to contend with the shortcomings of this tech. For example, you will clearly see a colour shift when viewed at an angle. This apart, the brightness is pretty decent and I could see it clearly even in the extremely hot Delhi sun. Talking about the bright Delhi sun, you can actually see the embedded sensor very clearly when you crank up the brightness. I don’t necessarily think it is a distraction, but I hope that display tech improves in the future to eliminate this issue.

All in all, the display on the Vivo X21 is where all the action happens. And that in-display fingerprint scanner is truly magical but needs a lot of work. But, what’s surprising is that no other big name manufacturer like Apple, Samsung, or LG has managed to pull this off. Well, Huawei did include an in-display fingerprint sensor in its newly launched Mate RS Porsche design, but can anyone really afford it?

Vivo X21 product shot 5

Vivo X21 design: Vivo V9’s twin

As far as the design of the Vivo X21 is concerned, it looks nearly identical to the Vivo V9. However, there are subtle changes that make a whole world of difference; both negatively and positively. 

Firstly, the X21 is actually made of glass and not plastic. Therefore, it adds a bit of heft making it easier to hold despite the slimmer 7.4mm profile (compared to the 7.9mm thickness of the V9). The most annoying thing about the design is the fact that Vivo is persisting with micro-USB port instead of Type-C one. There’s clear dichotomy at play here: at one end the X21 is the beacon of the future with its in-display fingerprint sensor, and at the other it refuses to let go of the past. 

Vivo X21 product shot 9

Thanks to the use of glass, the phone is slippery but the Black variant sent to Mr. Phone for review was not as big of a smudge magnet as I expected it to be. That’s a good thing. Vivo bundles a really good looking case inside the box, one that needs no replacement. The minimalistic rear of the phone, sans the physical fingerprint reader, makes it pretty attractive. Also interestingly, Vivo has put the SIM card tray at the bottom edge. This hybrid tray accepts two Nano SIM cards and you can swap out one SIM card for a microSD card, if you wish. 

Also read: Vivo V9 review: now you can afford an iPhone X

To sum up the design, the X21 is the V9’s shinier twin, one that will get all the attention.

Vivo X21 software: still needs work

Like the V9, the X21 also runs Android 8.1 with Vivo’s FunTouch OS 4.0 skin on top of it. Yup, it still looks like a copy of iOS. I have reviewed FunTouch OS 4.0 at length, and have also highlighted what I like and don’t like in my review of the V9

That said, I have one very important gripe to raise. Vivo’s software engineers still haven’t figured out a way to solve how content will play on the notch with navigation gestures on. So what happens is, when you decide to use navigation gestures, a bar remains like a sticky at the bottom. Take a look at the white bar in the image below. 

Vivo X21 product shot 2

Basically, FunTouch OS has a cordoned off a block of approximately 70 pixels for the navigation gestures at the bottom. I can’t understand why the software couldn’t hide it, like it does when you use on-screen capacitive buttons. Now, there are two ways to view videos and photos, and play games, in landscape mode. One, in a Safe Area mode and another where it takes the full screen. But, does it really? Nope. In fact, the white bar at the bottom persists. So apart from the chin, you also get a white space. It looks really distracting. And moreover, there is no way to turn off the notch. It just makes for a very weird viewing experience, one that I am not a fan of. 

Therefore, despite the existence of gestures, I had to use the navigation keys instead. Please fix this soon Vivo. 

Also, one software feature that is different compared to the V9 is the Always On display settings. You can change the style of the clock to analogue or digital. And you can also showcase phone call and messages notification on the screen. Unfortunately, it cannot show notifications from your email, Whatsapp, or any other third-party apps for now. 

Here’s an interesting thing though, the X21 is one of the very few phones that come with support for Android P beta. I haven’t had a chance to test out if it supports the Indian variant too. I’ll update the review once I test that. 

Vivo X21 product shot 5

Vivo X21 camera: surprisingly, the rear camera is better than the front

The X21 comes with two cameras on the rear – 12MP+5MP. The secondary 5MP camera is used for depth sensing. The 12MP camera comes with a lens which has an aperture of f/1.8 and uses dual pixel technology. What this means is that Vivo uses two photodiodes on the same pixel for faster focussing. Also, the new 12MP sensor has a pixel size of 1.44 microns. This means that you can expect to shoot good photos from the X21. And you know what, it actually delivers. 

P.S. Click on the image to see the full resolution sample.

vivo x21 14

I managed to shoot some good looking shots in ideal lighting conditions. You will see extremely punchy colours that look good on any display. Obviously, the colour accuracy is not ideal but a lot of folks will like how this looks. The problem with the camera is actually the focussing speeds, which is weird. Vivo actually claims faster focussing speeds but I had to stay stable to get a shot without a blur. That apart, I really liked the new 12MP camera on the rear because it also takes good HDR shots as well. Take a look at these samples below.

vivo x21 7

HDR off

vivo x21 8


The portrait mode on the X21 lets you adjust the focal length before shooting and after too. According to me, the sweet spot for getting a good blur is f/4. It works well in my opinion. I have no qualms. The low light shots are not bad either but definitely not the best in class. The software algorithm works overtime to reduce the noise and as a result ends up smudging a lot of the details. But this is the case with a lot of mid-range phones and therefore one can’t complain. vivo x21 3

The camera can capture 4K video but my test sample had a weird pink tint and since there is no EIS for 4K videos, it was pretty shaky too. On the contrary, the quality of the 1080p video was pretty good with good details across the board. You also get EIS out of the box for 1080p footage and that’s definitely an advantage. 

vivo x21 2 vivo x21 16

This is where things get interesting. The front facing camera also uses the same 12MP sensor as the rear camera. While it does take good selfies, the problem is that even without Beauty Mode on, it makes my face look fairer than usual. A lot of folks might like this, but I am not a fan. Oh, and before I forget, you get AI-based stickers on the phone which can be used to make some fun selfies. I like these stickers, they look as good as Snapchat’s stickers. 

vivo x21 15

Vivo X21 performance: rock solid

The Vivo X21’s internal kit comprises of a solid combination of hardware which includes: a Qualcomm Snapdragon 660 SoC, 6 gigs of RAM, and 128GB of internal storage (expandable up to 256GB using a microSD card). While the 660 is a super mid-range chip, it is very powerful as we’ve learnt from the Nokia 7 Plus. In fact, apart from the 660, the rest of the specs are flagship-grade. 

Also read: Nokia 7 Plus review: I would buy this phone in a heartbeat

In my time with the phone, I didn’t face a single slowdown and the X21 is an extremely responsive phone. One way to test the phone’s performance prowess is to scroll through your Facebook feed in the official app. No, I am not kidding. The app is so poorly coded that low-end chipsets struggle to keep up with the scrolling speed. The X21 has no problems whatsoever. And as far as gaming is concerned, I played Guns of Boom, Shadowgun Legends, and PUBG – all of which are graphically intensive games. All the games ran without any smoothly without any frame drops. While PUBG chooses the medium graphics setting by default, I pushed it to high and still didn’t face any problems. The phone doesn’t heat up while gaming either. The X21 scored 1,32,674 in AnTuTu and had a multi-core score of 5378 in Geekbench, which is great. 

Vivo X21 product shot 4

Moving on to the audio quality, the X21 includes a “hi-fi” DAC. Unfortunately, I couldn’t find the actual model of the DAC being used but in my testing I found that it could power my 1More Triple Driver with ease. In fact, the sound was pretty clean without any artefacts as such. However, the single downward firing mono speaker doesn’t get very loud and the sound gets muffled easily when it is covered by your palm. 

As far as the call quality is concerned, I am extremely impressed by the X21. I got a stable Airtel network with crystal clear calls even in high congestion areas. Furthermore, I didn’t face any call drops either. Also, the phone app lets you record calls, which could come in handy for a lot of folks. For those wondering, the X21 has support for Dual-VoLTE as well. 

Powering all this is a 3,200mAh battery with support for fast charging. Vivo calls it Dual Engine Quick Charge. And boy, is it fast! I can’t believe that it is as fast as OnePlus’ Dash Charge. Additionally, I got an average SoT of around 5 hours and 20 minutes, which is not bad but not great either. Basically, you can expect a days worth of usage from the phone. Not including wireless charging despite having a glass body is definitely a missed opportunity.  

Vivo X21 product shot 11

Should you buy the Vivo X21?

If you are considering the X21, you have to be an early adopter. None of my friends and family could comprehend the importance of the under-display fingerprint scanner. But let me tell you this, the in-display sensor is a very, very big advancement in the field of mobile tech. 

But, the price of Rs 35,999 is a steep for a phone with a 660 SoC. I find it difficult to recommend it over the OnePlus 6, which is by far the best phone right now in this price range. That said, the X21 is a great first attempt at showcasing tech that no other brand has figured out yet. Kudos, Vivo. 

Also read: OnePlus 6 review: upholds its legacy of being the fastest phone on the planet

What do you think about the X21? Let us know in the comments section below 

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Ershad Kaleebullah

When Ershad isn't writing, he spends time killing virtual zombies on his PS4. Having worked with a slew of renowned publications like PCWorld, Channelworld, CIO, NDTV Gadgets (now Gadgets360), MySmartPrice, The Inquistr, and 91Mobiles, Ershad brings a whole world of experience to Mr. Phone. He is trying hard to convert all the team members into Apple fans but is facing a lot of resistance. Is anyone willing to help?