ASUS Zenfone 9 review: Great things come in small packages

ASUS offered two models in the Zenfone series last year: the standard Zenfone 8 was aimed at those looking for a small phone, and it was joined by the Zenfone 8 Flip that had a 6.67-inch panel and 5000mAh battery. This year, however, ASUS is going all-in on the small form factor, launching just a single variant of the Zenfone 9 that focuses on one-handed usability.

To that effect, the Zenfone 9 is a little narrower and shorter than its predecessor, making it the ideal device for one-handed use. At the same time, ASUS retained the same 5.9-inch 120Hz screen, somehow increased the battery, and added huge camera modules at the back and a thermal cooling layer that's in line with that you'll find on $1,000 flagships.

ASUS hasn't removed any features either; the Zenfone 9 still has IP68 dust and water resistance, great stereo sound, and there's even a 3.5mm jack. And on the hardware side of things, it features Qualcomm's latest Snapdragon 8+ Gen 1 platform. The small flagship category has constricted in recent years, but with the Zenfone 9, ASUS has delivered a device that raises the bar for this segment.

About this review

I'm writing this review after using the Zenfone 9 as my daily driver for ten days in Hyderabad, India. I'm using the 16GB/256GB version of the phone, and it runs Zen UI based on Android 12 along with the June 2022 security update. It received an OTA update out of the box to build 32.2004.2004.78, and a further update on the day I'm publishing this review (July 28) to build 32.2004.2004.84 containing stability and bug fixes alongside camera tweaks. ASUS provided the unit to Android Central for review.

ASUS Zenfone 9: Price and availability

ASUS unveiled the Zenfone 9 on July 28, 2022, and the phone will go up for sale in August. It will debut in Taiwan, Hong Kong, and Europe initially, where the Zenfone 9 will cost €799 ($815). Like last year, ASUS will introduce the Zenfone 9 in the U.S., but the brand didn't reveal a launch date as of yet. The good news is that the phone will launch for $699 in the U.S., making it that much more affordable.

The Zenfone 9 will be sold in three configurations: a base model that comes with 8GB of RAM and 128GB of storage, an 8GB/256GB version, and a 16GB/256GB edition. The last variant seems overkill given you don't need 16GB of RAM, and it would have been better to see a 512GB storage variant instead. You can choose between four interesting color options this time around.

ASUS Zenfone 9: Design

There's a clear shortage of short phones with flagship internals, and that's the area ASUS is targeting with the Zenfone 9. As such, you get a diminutive design that makes other compact devices like the Pixel 6a and Xiaomi 12 Lite look huge. The Zenfone 9 is smaller even than its predecessor, with dimensions of 146.5 x 68.1 x 9.1mm.

What this means is that the Zenfone 9 is an absolute joy to use one-handed. It's 2.5mm narrower than the Galaxy S22, and the difference is noticeable in daily use. It is 1.5mm bulkier, but on the plus side, you get a large 4300mAh battery. And while most small phones tend to be focused on the mid-range category, that isn't the case with the Zenfone 9 — this is one of the fastest phones you can buy today.

A key difference from last year is the switch to a rectangular design with flat sides; ASUS noted that this was the best way to maximize the internal volume. While I'm not a fan of this trend, I didn't have issues on the Zenfone 9; for one thing, the phone's dimensions ensured it nestled easily in my hand, and there's a subtle curve where the back meets the mid-frame, and that makes a sizeable difference with the in-hand feel.

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ASUS went with an aluminum mid-frame that has a matte finish, and it's great to hold and use. As for the design at the back, two things stand out: a gigantic camera housing that takes up a significant chunk of room, and a new textured material that feels much better than polycarbonate. Although the device is using a metal mid-frame, it comes in at 169g, and that's thanks to the new polymer material used at the back.

Let's talk a little bit more about that camera housing, because it is one of the largest I've seen on a phone this year. The Zenfone 9 has two cameras, each ensconced within its own ring, and the main 50MP module protrudes quite a bit from the body of the device, making it wobble on a flat surface.

I'm no stranger to using phones with bulky camera designs — I used the Xiaomi 11 Ultra for several months last year — but the sheer size of the modules here makes them seem out of proportion with the rest of the device. This is because ASUS went with large cameras and gimbal stabilization tech; a first for the manufacturer. The result is that the two cameras take up an inordinate amount of room at the back.

The design for the camera housing may not be to everyone's liking, but ASUS nailed the rest of the design brief. The polymer material that ASUS designed for the back is 36% lighter while still delivering excellent grip, and the finish ensures it's easy to hold. That said, the black color variant isn't quite as effective at hiding smudges or scratches, and you should consider one of the other colors if you intend to use the Zenfone 9 without a case.

There's good news on that front, as ASUS is offering the Zenfone 9 in four color variants: Midnight Black, Moonlight White, Starry Blue, and Sunset Red. The red and blue options in particular look incredible, and that would be the way to go for this device. The material itself isn't as immune to scratches as glass, but ASUS says that it should be more durable.

Another area where ASUS switched things up this time is biometrics. The Zenfone 9 has a side-mounted fingerprint sensor in lieu of an optical in-screen module like last year's Zenfone 8. My only issue with it is that it's positioned slightly lower than where my thumb usually rests when using the phone one-handed, and it would have been better to just have the power button on the right and the volume rocker on the left.

That said, the sensor itself is noticeably faster than in-screen solutions, and I didn't have any issues with authentication. The side-mounted key doubles up as a multi-function button that lets you pull down the notification shade (a very nifty addition and one I used a lot), control media playback, launch Google Assistant, and so much more. As is often the case with ASUS, you get an extensive set of customization options for the button — you can set up slide, double press, and long press and hold actions for the key.

In a similar vein, ASUS also includes a double tap gesture at the back that can be used for toggling the flashlight on or off, launching Google Assistant or the camera, and controlling media playback. The side-mounted button and the back gesture go a long way in making the Zenfone 9 that much more convenient to use one-handed.

Oh, and there's a 3.5mm jack located at the top. It's incredulous to me that ASUS managed to fit the analog jack in this phone while Samsung didn't bother with it on the Galaxy S22 Ultra, a device that's 16.8mm taller and a full 9.8mm wider. Best of all, the Zenfone 9 gets IP68 dust and water resistance, making it immune to a dunk in the pool or the tub.

Overall, ASUS did a brilliant job with the design of the Zenfone 9. If you want a small Android phone that's great to hold and use and doesn't miss out on any of the extras that the best Android phones offer, this is the obvious choice.

ASUS Zenfone 9: Screen

The Zenfone 9 comes with a 5.9-inch Samsung AMOLED panel with an FHD+ (2400 x 1080) resolution, 120Hz refresh rate, and HDR10+. This is the same panel ASUS went with last year on the Zenfone 8, and you get a layer of Corning Gorilla Glass Victus. The screen goes up to a maximum of 800 nits in daily use and 1100 nits for HDR content, and I had zero issues with outdoor visibility.

That said, there were a few scenarios where the ambient light sensor took a few seconds to adjust the screen's brightness. This is usually the case right after unlocking the screen, and I found that the brightness was set to a lower limit than what was needed for the ambient light. It's not anywhere as faulty as the Nothing phone (1), but I didn't notice this particular issue on the Zenfone 8, so it's worth mentioning. 

Other than that quibble, the screen is a delight to use. It has excellent colors and contrast levels, and like the Find X5 Pro, the panel is calibrated to a Delta-E<1 color accuracy at two brightness levels, giving you better colors with the brightness turned down. There's no dynamic refresh tech here, but you can choose between 60, 90, and 120Hz modes. There's a decent amount of customizability as well, including an always-on feature that's similar to what you get on the Pixels.

ASUS always does a great job optimizing its phones, and that's no different here. I switched to the Zenfone 9 after using the phone (1) and Pixel 6a, and it makes those devices feel slow. There's a level of immediacy with every interaction that you just don't get on other devices, even Samsung flagships — it reminds me of OnePlus in its heyday.

Another standout is the onboard audio. The stereo sound you get here is loud, detailed, and free of any distortion. ASUS once again went with Dirac for the tuning of the audio, and you get the brand's AudioWizard tuning engine that gives you a 10-band EQ and customized modes for gaming, movies, and day-to-day use. The 3.5mm jack uses Qualcomm's Aqstic WCD9385 DAC to deliver 32-bit 384kHz playback when using Hi-Res branded audio gear.

ASUS Zenfone 9: Performance

ASUS is in the first wave of manufacturers to release devices featuring Qualcomm's latest Snapdragon 8+ Gen 1 chipset, and that allows the Zenfone 9 to stand out just that bit more in the value flagship category. The Snapdragon 8+ Gen 1 is particularly interesting as it fixes one of the biggest issues with the Snapdragon 8 Gen 1: energy efficiency.

The standard 8 Gen 1 is power hungry and devours batteries, and this is the case with all 2022 flagships that feature the platform. A big part of the issue has to do with Samsung LSI's 4nm node; it doesn't deliver any meaningful efficiency gains over the 5nm node, and with Qualcomm increasing the frequencies of its performance gains this generation, the 8 Gen 1 needs to throttle earlier to conserve power. 

Qualcomm mitigated the issue by switching to TSMC for the 8+ Gen 1; without going into the weeds too much, all I'll say is that TSMC's 4nm manufacturing node delivers much better efficiency.

The numbers speak for themselves: the Snapdragon 8+ Gen 1 delivers a noticeable 10% uptick in GPU and CPU performance, but it's the efficiency that turns it into a spectacular offering. For the same workloads, the 8+ Gen 1 consumes 30% less power than the 8 Gen 1, and that's an astounding figure when you consider Qualcomm didn't have to change the underlying architecture at all.

Anyway, what all of this means is that the Zenfone 9 delivers much better performance than just about any Android phone in the market today, and it does so while consuming less power. It's this efficiency that allowed ASUS to retain a small chassis while still delivering battery life in excess of a day.

To give you a car analogy, this is equivalent to Volkswagen putting a massive V12 engine in a Golf. Of course, the Golf cannot use anywhere close to the full potential of that V12 as it's front-wheel drive and will just spin the tires out. Thankfully, the Zenfone 9 is able to put that power down meaningfully. Here's a look at some synthetic scores:

As you can make out, the Snapdragon 8+ Gen 1 pulls into a significant lead in just about every category, and the fact that it does so while being more energy-efficient makes it the runaway leader on Android. That's evident when using the Zenfone 9; this is one of the fastest phones I used this year, and ASUS did a great job with the optimization — there's no lag or slowdowns anywhere in the interface.

The Zenfone 9 holds its own during gaming as well, delivering smooth framerates in visually demanding titles without breaking a sweat. I don't foresee this device slowing down for several years; as it is, the 8+ Gen 1 is overkill for most daily tasks and gaming. ASUS also added a large thermal cooling material at the back that makes a significant difference when gaming.

The device gets hot during extended gaming sessions, but it isn't the back where you'll feel the heat; the metal mid-frame gets hotter instead. The back of the phone got up to 39.2 degrees Celsius, and the sides were at 40.4 degrees — hot enough to be uncomfortable. This is with the High Performance mode activated; if you switch to the Dynamic mode, it doesn't get as hot, and I didn't see any issues with throttling either.

Continuing with the hardware, the Zenfone 9 comes with 8GB of RAM and 128GB of storage as standard, and you'll find a version with 8GB of RAM and 256GB of storage, and an insane 16GB of RAM and 256GB of storage. I'm using the 16GB/256GB model, and I don't really understand ASUS's motives behind doubling the RAM and not the storage instead. There's just no meaningful way that 16GB of RAM is useful in a device other than bragging rights, but 512GB of storage would have been a definite bonus. ASUS says it won't release any additional variants of the device, so if you're eyeing this phone, the 8GB/256GB option is the way to go.

The Zenfone 9 isn't missing out on the connectivity front. You get Wi-Fi 6e, Bluetooth 5.2, LDAC, and the AptX Adaptive codecs, and there's NFC, dual-SIM connectivity as standard, and dual-band GPS. You'll find a decent selection of Sub-6 5G bands as well: n1/2/3/5/7/8/12/20/25/28/38/40/41/66/71/77/78. I didn't see any issues whatsoever with Wi-Fi 6 or cellular connectivity, but my unit had a defective mic. The phone has two mics — one at the top and the other at the bottom — and the one at the bottom is used predominantly for calls. This was the defective one, so my Zenfone 9 was unusable for video calls and voice calls with the speaker enabled.

ASUS sent all four colors of the Zenfone 9, but I didn't get my hands on the other units in time for the review, so I'll switch to one of the other variants once they show up and find out if they have a similar issue. I flagged the problem to ASUS and was told that it could just be a hardware defect with my unit, and that it didn't hear of this particular issue from other reviewers.

Elsewhere, the vibration motor is strong and delivers great feedback, and you get the ability to adjust the intensity of the motor for various daily use cases. You won't find a MicroSD card here, but other than that, there isn't a single area where the Zenfone 9 is found lacking on the hardware front.

Given its size, it's incredible just how powerful the Zenfone 9 is in daily use, and if you've been waiting to get your hands on a small phone that delivers unbelievable performance, this is the one to get.

ASUS Zenfone 9: Battery

The biggest issue with a small phone is battery life. Thankfully, that isn't an area of worry for the Zenfone 9. The phone has a 4300mAh battery, and has 30W fast charging over the USB PD 3.0 standard — ASUS bundles a 33W charger in the box. While it isn't as fast as the 65W or 80W standards you get in this category, it is reliable.

As for battery life itself, the Zenfone 9 easily manages to last well over a day without any issues. Even with heavy use with over six hours of screen-on-time spread out over the course of 18 hours, the phone had plenty of power left over, and I didn't see the charge go below 20% at any time. More often than not, I was able to get two days out of the battery, averaging three hours of SOT each day.

In short, there's absolutely no battery anxiety with the Zenfone 9, and the device does a great job in this area. ASUS has a few features to extend battery longevity; you can set a custom charging limit so the charge doesn't go over 90%, and there's scheduled charging to slowly charge the battery when plugging it in overnight.

ASUS Zenfone 9: Cameras

ASUS didn't really focus a whole lot on the camera side of things in the last two years, and that was evident with the Zenfone 7 and Zenfone 8 series. That's changing with the Zenfone 9; the phone has a 50MP f/1.9 Sony IMX 766 sensor with OIS and 6-axis gimbal stabilization, with 1.0um pixels and the ability to shoot 8K video. The main lens is joined by a 12MP f/2.2 Sony IMX 363 wide-angle shooter with 1.4um pixels and a 113-degree field of view. At the front, there's a 12MP f/2.4 Sony IMX 663 module with a 76.5-degree field of view and autofocus.

The Sony IMX 766 is a stalwart in this category, and is featured in the likes of the Find X5 Pro, Xiaomi 12 Pro, Nothing phone (1), and others. There are a lot of phones that use the sensor, with most manufacturers able to tune it well enough to deliver its full potential, while others have struggled to do so. For its part, ASUS managed to do a great job tuning the cameras on the Zenfone 9.

But before we get to that, a note on the gimbal stabilization. Vivo pioneered gimbal tech in phones over the last two years, and ASUS is following a system wherein the entire camera assembly is on the stabilizer, and you can see the module moving when shooting videos. 

ASUS says the stabilization corrects up to three degrees of motion, and it makes a noticeable difference in daily use. The gimbal stabilization tech works up to the full potential of the sensor itself, so you can shoot 8K video at 24fps or 4K at 60fps with the stabilization enabled. Additionally, you get a HyperSteady mode that kicks things up a gear, but it only works in 1080p and goes up to 60fps.

The camera interface itself isn't too different to other brands, with the shooting modes laid out in a ribbon at the bottom. You can change the layout of the modes, and ASUS is debuting a Light Trail mode that lets you shoot traffic trails, waterfalls, and so on. There's also a Pro mode that lets you manually adjust focus, ISO, and other parameters, and there's the ability to shoot in RAW as well.

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It's clear that ASUS put a lot of thought into the cameras this year, as daylight shots taken with the Zenfone 9 come out with great dynamic range and excellent detail. Colors tend to be a bit too saturated, but foliage is clearly differentiated into various hues of green, you get natural skin tones, and overall, it is on par with the Galaxy S22 in this regard.

The biggest difference is with low-light shots; the Zenfone 9 manages to deliver accurate colors while still able to manage highlights so you don't miss out on finer details. There's still visible noise in shots, but the dedicated Night mode does a great job in such situations, delivering cleaner shots. 

This is particularly useful in conjunction with the wide-angle shooter; the 12MP module by itself isn't quite as good as the 50MP primary lens, but you can eke out much more detail by switching to the Night mode. The wide-angle lens takes good photos in daylight situations, delivering the same color balance as the main lens. In a similar vein, I didn't have any issues with the front camera; it focuses on a subject fast enough, and the resultant photos are vibrant and full of detail. The Zenfone 9 also does a fantastic job with video, and the gimbal stabilization tech makes a tangible difference when shooting handheld.

Overall, the camera isn't quite on par with devices that have massive sensors — like the Galaxy S22 Ultra and the Xiaomi 12S Ultra — but it holds its own against other phones in this category that feature the same Sony IMX 766 hardware, such as the Xiaomi 12 and Find X5. And that in itself is a big achievement for ASUS considering how the Zenfone 8 fared in this area last year. The standout addition this year is gimbal stabilization; it adds another dimension to what is already a great camera, making the Zenfone 9 a noteworthy choice for videos as well as photos.

ASUS Zenfone 9: Software

ASUS is doing a lot of right things on the software front. The Zenfone 9 runs Zen UI based on Android 12 out of the box, and ASUS doesn't offer any overt customization of the interface itself. That's a good thing, as the vanilla Android interface is a delight to use, particularly on a device this powerful. You get the Material You interface with the dynamic color picker and all the features Google introduced with Android 12, and ASUS has its own meaningful additions, like the customization with the side-mounted ZenTouch side key and aforementioned gestures.

You won't find any bloatware either, but in a puzzling mode, ASUS offers its own alternative to Google's dialer, calendar, contacts, and so on. Most manufacturers now use Google's services as standard here, and other than Samsung, no brand is still bundling its own dialer. That said, you get the option to switch to Google's dialer, and for what it's worth, you can disable ASUS's alternatives to these utilities.

Overall, it's very enjoyable to use Zen UI. The Zenfone 9 by itself is great for one-handed use, and there's a one-handed mode that lets you shrink the screen size further. You also get floating windows, the ability to use two instances of an app, battery management features that actually work without being too aggressive, and so on. I usually have issues with push notifications with Newton Mail whenever I sign in to a new device for at least a few days, but that wasn't the case here.

The only issue I have with the software is the update situation. ASUS will only deliver two Android OS updates and two years of security updates to the phone, and that is less than the industry standard. With other manufacturers guaranteeing three Android updates and four years of security patches, ASUS is distinctly on the backfoot here, and it needs to alter its stance. If nothing else, the hardware on offer is more than adequate for several years' worth of use, and you shouldn't have to switch to a new phone because it doesn't get the requisite number of software updates.

ASUS Zenfone 9: The competition

There's no shortage of alternatives if you want a phone for $700. The Galaxy S22 continues to be a great overall choice for its design, feature-set, and the fact that it is also designed for one-handed use. The phone has a larger 6.1-inch 120Hz AMOLED screen, all-day battery life, powerful hardware, and cameras that take great photos in any situation. You also get a zoom lens here with 3x optical zoom, and while there's wireless charging, the battery itself isn't as large as the one on the Zenfone 9. But the biggest differentiator for Samsung is that the Galaxy S22 will get four guaranteed Android OS updates — two more than what ASUS is offering.

If you're in a country where the Xiaomi 12 is available, it is a good alternative. It is slightly larger than the Zenfone 9 but still suitable for one-handed use, and you get great hardware combined with a minimalist design, 120Hz AMOLED screen with a lot of customizability, stereo sound, and standout cameras. The Xiaomi 12 has a larger 4500mAh battery and includes wireless charging, but you miss out on IP68 dust and water resistance. As for the software, MIUI 13 is fast and fluid, and Xiaomi did a good job reducing the bloatware. The Xiaomi 12 will get three Android OS updates, and while Xiaomi doesn't go a great job rolling these out on time, it is more than what you get with the Zenfone 9.

ASUS Zenfone 9: Should you buy it?

You should buy this if:

• You want a small phone with flagship internals
• You're looking for a value flagship with great cameras
• You want a phone with clean software
• You need a 3.5mm jack and IP68 rating
• You're looking for a small phone with two-day battery life

You shouldn't buy this if:

• You want long-term software updates
• You need wireless charging

I liked the Zenfone 9 more than I thought I would, and that's entirely down to its diminutive size. After using the likes of the Galaxy S22 Ultra, Find X5 Pro, and the Pixel 6 Pro, it's great to switch to a small phone that offers the same feature-set and fluidity in daily use. ASUS's decision to use the latest Qualcomm silicon makes the Zenfone 9 one of the fastest phones in the market today, and that's evident the moment you start using the device — there's a level of performance on offer here that you don't get on many flagships.

But that's not the only highlight here. The Zenfone 9 delivers in all other areas as well; the 120Hz AMOLED screen is ideal for gaming or streaming videos and day-to-day browsing, the cameras are the best I've used on any Zenfone to date, and the phone lasts well over a day even with heavy use. I also like what ASUS is doing on the software side of things; Zen UI offers a clean and uncluttered interface that's a joy to use, and you get meaningful additions that go a long way. 

The only downside here is that the Zenfone 9 will get just two platform updates; that's annoying when you consider the hardware on offer and the fact that you can easily use the phone for four to five years without seeing any noticeable slowdowns.

ASUS says that engineering resources constrains are the reason it can only deliver two platform updates to its phones, but when you consider that all other phones in this category will get at least one more Android OS version update than the Zenfone 9, it is a letdown. That said, there really isn't another device that quite manages to deliver the combination of hardware, cameras, and clean software in such a small chassis, so if you're still on the lookout for a small flagship, your search ends here.