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Asus Zenfone 4 Pro ZS551KL (6GB + 128GB) Review | 197 Data compared

Avg. price:~£750RAM capacity:6 GBInternal storage:128 GBScreen size:5.5 inchesMain camera megapixels:16 MP & 12 MP

Asus Zenfone 4 Pro ZS551KL (6GB + 128GB) Review: Compare 197 technical specifications and user reviews to see how this product ranks in the Smartphones category and whether it is worth buying.

5.6/10

Overall score

Score
5.6/ 10
✕
What it is
An overall evaluation of the smartphone's quality, based on technical analyses and user reviews.
When it matters
When you need a quick reference to identify the best smartphones on the market.
Score distribution
â–¼
<55-66-77-88-99-10
â–¼ Worse than 90% of models
Score components

90%

5.6

Technical score

10%

?

User score

â–¼Worse than 90% of smartphones
5.9

Value for money

Value for money
5.9/ 10
✕
What it is
An indicator that combines the smartphone's overall rating with its cost.
When it matters
When you are looking for a smartphone with a good balance between quality and price.
Score distribution
â–¼
<55-66-77-88-99-10
â–¼ Worse than 99% of models
Score components

70%

5.6

Overall score

30%

6.6

Price

â–¼Worse than 99%
5.6

Technical score

Technical score
5.6/ 10
✕
What it is
An assessment of the smartphone's technical performance, covering eight key areas: performance & hardware, software, camera, connectivity, display, battery, audio, and design.
When it matters
When you want to compare smartphones based on technical performance and available features.
Score distribution
â–¼
<55-66-77-88-99-10
â–¼ Worse than 84% of models
Score components

25%

5.8

Performance & Hardware

18%

7.2

Camera

15%

4.9

Display

15%

5.0

Battery

10%

3.0

Software

10%

6.7

Connectivity

4%

5.7

Audio

3%

7.1

Design

â–¼Worse than 84%
?

User score

User score
8.0/ 10
✕
What it is
A rating that combines user reviews and the total number of reviews received by the smartphone
When it matters
When you want to know how a smartphone handles daily tasks and how reliable it remains over time according to user feedback.
Score distribution
â–¼
<55-66-77-88-99-10
â–¼ Worse than 70% of models
Score components

70%

?

User ratings

30%

?

Number of reviews

  • No image
No image
Where to buy
    N/A~ £750
Best rankings
Available: ranking among products currently available (including other versions of this product).All: ranking among all products in the database.
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Technical Specifications of smartphone Asus Zenfone 4 Pro ZS551KL (6GB + 128GB)

Technical score
Technical score
5.6/ 10
✕
What it is
An assessment of the smartphone's technical performance, covering eight key areas: performance & hardware, software, camera, connectivity, display, battery, audio, and design.
When it matters
When you want to compare smartphones based on technical performance and available features.
Score distribution
â–¼
<55-66-77-88-99-10
â–¼ Worse than 84% of models
Score components:

25%

5.8

Performance & Hardware

18%

7.2

Camera

15%

4.9

Display

15%

5.0

Battery

10%

3.0

Software

10%

6.7

Connectivity

4%

5.7

Audio

3%

7.1

Design

5.6
User score
User score
8.0/ 10
✕
What it is
A rating that combines user reviews and the total number of reviews received by the smartphone
When it matters
When you want to know how a smartphone handles daily tasks and how reliable it remains over time according to user feedback.
Score distribution
â–¼
<55-66-77-88-99-10
â–¼ Worse than 70% of models
Score components

70%

?

User ratings

30%

?

Number of reviews

?
Popularity
Popularity
1.0/ 10
✕
What it is
An indicator based on the number of reviews received by the smartphone.
When it matters
When you prefer to purchase a product chosen and reviewed by many other consumers.
Score distribution
â–¼
<55-66-77-88-99-10
â–¼ Worse than 99% of models
Popularity:
Asus Zenfone 4 Pro ZS551KL (6GB + 128GB) has a popularity of 1 point, which is lower than 63.9% of smartphones.
1.0
Value for money
Value for money
5.9/ 10
✕
What it is
An indicator that combines the smartphone's overall rating with its cost.
When it matters
When you are looking for a smartphone with a good balance between quality and price.
Score distribution
â–¼
<55-66-77-88-99-10
â–¼ Worse than 99% of models
Score components:

70%

5.6

Overall score

30%

6.6

Price

5.9
Brand name
Asus
Processor model
Qualcomm Snapdragon 835
This smartphone uses the Qualcomm Snapdragon 835 processor model which is slower than processors in 68.7% of smartphones and equal to processors in 0.7% of smartphones.
RAM capacity
6 GB
Market range: <4 GB – >16 GB
This smartphone has a RAM capacity of 6 GB which is smaller than the RAM capacity of 71.8% of smartphones and equal to that of 10.8% of smartphones.
Internal storage
128 GB
Market range: <64 GB – >512 GB
This smartphone has an internal storage capacity of 128 GB which is smaller than the storage of 61.2% of smartphones and equal to that of 28.4% of smartphones.
CPU boost clock speed
2.45 GHz
Market range: <2 GHz – >3.3 GHz
The CPU boost clock speed of this smartphone is 2.45 GHz which is higher than the boost speed of 50.2% of smartphones and equal to that of 0.7% of smartphones.
Show more
Operating system
Android
This smartphone uses the Android operating system, which outperforms that of 1%.
Android 7 Nougat
Android version
Android 7 Nougat
This smartphone runs Android version Android 7 Nougat which is older than that found in 98.4% of smartphones and equal to that in 0.8% of smartphones.
Direct OS updates
no
This smartphone does not receive direct OS updates. 20.6% of smartphones receive direct updates.
Open-source OS
yes
This smartphone uses an open-source OS. 94.6% of smartphones use an open-source OS.
Dark mode
no
This smartphone does not offer dark mode. 95.8% of smartphones support this feature.
Show more
Multi-lens main camera
yes
This smartphone includes a multi-lens main camera system. 93.7% of smartphones include multi-lens setups.
Main camera megapixels
16 MP & 12 MP
Market range: <10 – >100
This smartphone has a main camera resolution of 16 MP & 12 MP which is lower than that of 86.5% of smartphones and equal to that of 0.2% of smartphones.
Main camera aperture
f/1.7
This smartphone has a main camera aperture of f/1.7 which is wider than that of 79.1% of smartphones and equal to that of 0.7% of smartphones.
Main camera sensor area
31.4 mm²
Market range: <19.7 mm² – >71.4 mm²
This smartphone has a main camera sensor area of 31.4 mm² which is smaller than the main camera sensor area of 57.3% of smartphones and equal to that of 5.8% of smartphones.
Main camera pixel size
1.4 µm
Market range: <0.64 µm – >1.22 µm
This smartphone has a main camera pixel size of 1.4 µm which is larger than in 92.7% of smartphones and equal to the size in 4% of smartphones.
Show more
Number of SIM slots
2
Market range: <1 – >6
This smartphone has 2 SIM slots, which is more than in 3.8% of smartphones and equal to the number in 96.1% of smartphones.
Cellular module
yes
This smartphone includes a cellular module. 100% of smartphones include cellular modules.
5G connectivity
no
This smartphone does not support 5G connectivity. 66.9% of smartphones support 5G.
LTE support
yes
This smartphone supports LTE. 99.7% of smartphones include LTE connectivity.
Wi-Fi connectivity
yes
This smartphone supports Wi-Fi connectivity. 100% of smartphones offer Wi-Fi support.
Show more
Screen size
5.5 inches
Market range: <6.3 inches – >6.82 inches
This smartphone has a screen size of 5.5 inches which is smaller than the screens of 97% of smartphones and equal to those of 0.8% of smartphones.
Screen resolution
1080x 1920 px
This smartphone has a screen resolution of 1080x1920 px which is lower than that of 75.9% of smartphones and equal to that of 0.6% of smartphones.
Pixel density
401 ppi
Market range: <264 ppi – >460 ppi
This smartphone has a pixel density of 401 ppi which is higher than that of 58.5% of smartphones and equal to that of 3% of smartphones.
Display type
OLED/AMOLED
This smartphone uses a OLED/AMOLED display type. 58.6% of smartphones use this display technology.
Refresh rate
60 Hz
Market range: <60 Hz – >144 Hz
This smartphone supports a refresh rate of 60 Hz which is lower than in 84.3% of smartphones and equal to that in 15.7% of smartphones.
Show more
Battery capacity
3,600 mAh
Market range: <4k mAh – >7k mAh
This smartphone has a battery capacity of 3,600 mAh which is smaller than the batteries in 94.2% of smartphones and equal to those in 0.1% of smartphones.
Charging speed
18 W
Market range: <15 W – >90 W
This smartphone supports charging speeds of 18 W which is slower than in 76% of smartphones and equal to speeds in 11.7% of smartphones.
Fast charging
yes
This smartphone supports fast charging. 93.1% of smartphones support fast charging.
GSMArena full wired charge time
?
Wireless charging
no
This smartphone does not support wireless charging. 25.2% of smartphones support wireless charging.
Show more
Stereo speakers
yes
This smartphone includes stereo speakers. 64.4% of smartphones provide stereo audio.
3.5 mm headphone jack
yes
This smartphone includes a 3.5 mm headphone jack. 45.5% of smartphones offer this port.
Number of microphones
3
Market range: <1 – >3
This smartphone includes 3 microphones, which is more than in 77.2% of smartphones and equal to the number in 19.7% of smartphones.
FM radio
yes
This smartphone includes an FM radio. 34.2% of smartphones offer FM radio functionality.
aptX Lossless
no
This smartphone does not support aptX Lossless. 12.9% of smartphones provide aptX Lossless.
Show more
Height
156.9 mm
Market range: <156.2 mm – >171.56 mm
This smartphone has a height of 156.9 mm which is shorter than 88.7% of smartphones and equal to that of 0.1% of smartphones.
Width
75.6 mm
Market range: <73.1 mm – >81 mm
This smartphone has a width of 75.6 mm which is narrower than 57.6% of smartphones and equal to that of 1.9% of smartphones.
Thickness
7.6 mm
Market range: <7.53 mm – >10.5 mm
This smartphone has a thickness of 7.6 mm which is thinner than 86% of smartphones and equal to that of 3.5% of smartphones.
Weight
175 g
Market range: <175 g – >256 g
This smartphone weighs 175 g which is lighter than 89.9% of smartphones and equal to the weight of 0.8% of smartphones.
Device volume
81,900 cm³
Market range: <80 cm³ – >190 cm³
This smartphone has a device volume of 81,900 cm³ which is smaller than 91.2% of smartphones and equal to that of 0.1% of smartphones.
Show more

Asus Zenfone 4 Pro ZS551KL (6GB + 128GB) vs the average smartphone

246810TotalPerformance & HardwareSoftwareCameraConnectivityDisplayBatteryAudioDesign
  • Has optical image stabilization
    This smartphone has optical image stabilization (OIS), the average smartphone does not. 48.3% of smartphones feature OIS.
  • 2 x higher optical zoom
    This smartphone offers higher optical zoom than the average smartphone (2 x vs 0 x).
    2 x vs 0 x
  • 0.6 µm larger main camera pixel size
    This smartphone has a larger main camera pixel size than the average smartphone (1.4 µm vs 0.8 µm). The average pixel size is 0.8 µm.
    1.4 µm vs 0.8 µm
  • 50% lower TDP
    This smartphone has a lower TDP than the average smartphone (9 W vs 6 W). The average TDP for smartphones is 6 W.
    9 W vs 6 W
  • 2 more flash LEDs
    This smartphone has more flash LEDs than the average smartphone (3 vs 1). The average smartphone has 1 flash LEDs.
    3 vs 1
  • Wider front camera aperture
    This smartphone has a wider front camera aperture than the average smartphone (f/1.9 vs f/2.2). The average aperture is f/2.2.
    f/1.9 vs f/2.2
  • 1 more microphone/s
    This smartphone has more microphones than the average smartphone (3 vs 2). The average smartphone has 2 microphones.
    3 vs 2
  • Has a multi-lens front camera
    This smartphone features a multi-lens front camera, the average smartphone does not. 18% of smartphones have multiple front lenses.
  • 50% lower TDP
    This smartphone has a lower TDP than the average smartphone (9 W vs 6 W). The average TDP for smartphones is 6 W.
    9 W vs 6 W
  • Higher CPU base clock speed
    This smartphone has a higher CPU base clock speed than the average smartphone (4x2.45 GHz & 4x1.9 GHz vs 2x2.2 GHz & 6x2 GHz). The average smartphone has a base clock speed of 2x2.2 GHz & 6x2 GHz.
    4x2.45 GHz & 4x1.9 GHz vs 2x2.2 GHz & 6x2 GHz
  • 2.1% higher CPU boost clock speed
    This smartphone has a higher CPU boost clock speed than the average smartphone (2.5 GHz vs 2.4 GHz). The average smartphone has a boost clock speed of 2.4 GHz.
    2.45 GHz vs 2.4 GHz
  • 16.4% higher memory bandwidth
    This smartphone has higher memory bandwidth than the average smartphone (29.8 GB/s vs 25.6 GB/s). The average memory bandwidth is 25.6 GB/s.
    29.8 GB/s vs 25.6 GB/s
  • Has optical image stabilization
    This smartphone has optical image stabilization (OIS), the average smartphone does not. 48.3% of smartphones feature OIS.
  • 2 x higher optical zoom
    This smartphone offers higher optical zoom than the average smartphone (2 x vs 0 x).
    2 x vs 0 x
  • 0.6 µm larger main camera pixel size
    This smartphone has a larger main camera pixel size than the average smartphone (1.4 µm vs 0.8 µm). The average pixel size is 0.8 µm.
    1.4 µm vs 0.8 µm
  • 2 more flash LEDs
    This smartphone has more flash LEDs than the average smartphone (3 vs 1). The average smartphone has 1 flash LEDs.
    3 vs 1
  • Wider front camera aperture
    This smartphone has a wider front camera aperture than the average smartphone (f/1.9 vs f/2.2). The average aperture is f/2.2.
    f/1.9 vs f/2.2
  • Has a multi-lens front camera
    This smartphone features a multi-lens front camera, the average smartphone does not. 18% of smartphones have multiple front lenses.
  • Supports laser autofocus
    This smartphone features laser autofocus, the average smartphone does not. 21.4% of smartphones include laser AF.
  • Allows manual shutter speed
    This smartphone allows manual shutter speed control, the average smartphone does not. 29.8% of smartphones include this.
  • Supports HDR10 video recording
    This smartphone supports HDR10 video recording, the average smartphone does not. 35.9% of smartphones support HDR10.
  • Has an RGB LED flash
    This smartphone features an RGB LED flash, the average smartphone does not. 3.9% of smartphones include RGB flash.
  • Wider main camera aperture
    This smartphone has a wider main camera aperture than the average smartphone (f/1.7 vs f/1.8 & f/2.2 & f/2.4 & f/2.4). The average smartphone has a main camera aperture of f/1.8 & f/2.2 & f/2.4 & f/2.4.
    f/1.7 vs f/1.8 & f/2.2 & f/2.4 & f/2.4
  • Has an infrared sensor
    This smartphone includes an infrared sensor, the average smartphone does not. 33.3% of smartphones feature an IR blaster.
  • 1.5% higher pixel density
    This smartphone has a higher pixel density than the average smartphone (401 ppi vs 395 ppi). The average smartphone has a pixel density of 395 ppi.
    401 ppi vs 395 ppi
  • 1 more microphone/s
    This smartphone has more microphones than the average smartphone (3 vs 2). The average smartphone has 2 microphones.
    3 vs 2
  • Has a 3.5 mm headphone jack
    This smartphone features a 3.5 mm headphone jack, the average smartphone does not. 45.5% of smartphones include a standard headphone jack.
  • Has FM radio
    This smartphone features an FM radio, the average smartphone does not. 34.2% of smartphones include an FM tuner.
  • Supports aptX
    This smartphone supports aptX, the average smartphone does not. 50% of smartphones are aptX compatible.
  • 10.8% lighter
    This smartphone is lighter than the average smartphone (175 g vs 196.2 g). The average smartphone weighs 196.2 g.
    175 g vs 196.2 g
  • 6.7 mm shorter
    This smartphone is shorter than the average smartphone (156.9 mm vs 163.6 mm). The average smartphone height is 163.6 mm.
    156.9 mm vs 163.6 mm
  • 0.7 mm thinner
    This smartphone is thinner than the average smartphone (7.6 mm vs 8.3 mm). The average smartphone thickness is 8.3 mm.
    7.6 mm vs 8.3 mm
  • 16.3% smaller volume
    This smartphone has a smaller device volume than the average smartphone (81,900 cm³ vs 97,800 cm³). The average smartphone volume is 97,800 cm³.
    81,900 cm³ vs 97,800 cm³
  • Worse processor
    This smartphone uses a worse processor than the average smartphone (Qualcomm Snapdragon 835 vs Qualcomm Snapdragon 7 Gen 3).
    Qualcomm Snapdragon 835 vs Qualcomm Snapdragon 7 Gen 3
  • 50% lower refresh rate
    This smartphone has a lower refresh rate than the average smartphone (60 Hz vs 120 Hz). The average smartphone has a refresh rate of 120 Hz.
    60 Hz vs 120 Hz
  • No 5G connectivity
    This smartphone does not support 5G connectivity, the average smartphone does. 66.9% of smartphones are 5G compatible.
  • 28% smaller battery capacity
    This smartphone has a smaller battery capacity than the average smartphone (3,600 mAh vs 5,000 mAh). The average smartphone has a capacity of 5,000 mAh.
    3,600 mAh vs 5,000 mAh
  • 1.17 inches inch smaller screen size
    This smartphone has a smaller screen size than the average smartphone (5.5 inches vs 6.67 inches). The average smartphone has a screen size of 6.67 inches.
    5.5 inches vs 6.67 inches
  • 50% less storage
    This smartphone offers less internal storage than the average smartphone (128 GB vs 256 GB). The average smartphone includes 256 GB of internal storage.
    128 GB vs 256 GB
  • No live text recognition
    This smartphone does not support live text recognition, the average smartphone does. 50.9% of smartphones offer real-time text recognition.
  • Lower-resolution main camera
    This smartphone has a lower-resolution main camera than the average smartphone (16 MP & 12 MP vs 50 MP & 8 MP). The average smartphone has a 50 MP & 8 MP main camera.
    16 MP & 12 MP vs 50 MP & 8 MP
  • 23.9% worse value for money
    Asus Zenfone 4 Pro ZS551KL (6GB + 128GB) has worse value for money than the average smartphone (5.92 vs 7.3).
    5.92 vs 7.34
  • 2.88x more expensive
    Asus Zenfone 4 Pro ZS551KL (6GB + 128GB) is more expensive than the average smartphone (£750 vs £260).
    £750 vs £260
  • 5.44x less popular
    Asus Zenfone 4 Pro ZS551KL (6GB + 128GB) is less popular than the average smartphone (1 vs 5.4).
    1 vs 5.44
  • Worse processor
    This smartphone uses a worse processor than the average smartphone (Qualcomm Snapdragon 835 vs Qualcomm Snapdragon 7 Gen 3).
    Qualcomm Snapdragon 835 vs Qualcomm Snapdragon 7 Gen 3
  • 50% less storage
    This smartphone offers less internal storage than the average smartphone (128 GB vs 256 GB). The average smartphone includes 256 GB of internal storage.
    128 GB vs 256 GB
  • 25.3% slower GPU clock
    This smartphone has a lower GPU frequency than the average smartphone (710 MHz vs 950 MHz). The average smartphone has a GPU frequency of 950 MHz.
    710 MHz vs 950 MHz
  • 66.7% larger process node
    This smartphone is manufactured on a larger process node than the average smartphone (10 nm vs 6 nm). The average smartphone uses a 6 nm process.
    10 nm vs 6 nm
  • 70.9% fewer transistors
    This smartphone contains fewer transistors than the average smartphone (3,000 million vs 10,300 million). The average smartphone has 10,300 million transistors.
    3,000 million vs 10,300 million
  • 42.9% lower maximum RAM capacity
    This smartphone supports less maximum RAM than the average smartphone (8 GB vs 14 GB). The average smartphone supports 14 GB of RAM.
    8 GB vs 14 GB
  • 2 GB less RAM
    This smartphone has less RAM than the average smartphone (6 GB vs 8 GB). The average smartphone has 8 GB of RAM.
    6 GB vs 8 GB
  • 32.1% slower memory speed
    This smartphone has a lower memory speed than the average smartphone (1,866 MHz vs 2,750 MHz). The average smartphone has a memory speed of 2,750 MHz.
    1,866 MHz vs 2,750 MHz
  • 50% less L3 cache
    This smartphone has a smaller L3 cache than the average smartphone (2048 KB vs 4,096 KB). The average smartphone has an L3 cache of 4,096 KB.
    2,048 KB vs 4,096 KB
  • No live text recognition
    This smartphone does not support live text recognition, the average smartphone does. 50.9% of smartphones offer real-time text recognition.
  • Older Android version
    This smartphone runs an older Android version than the average smartphone (Android 7 Nougat vs Android 14). The average smartphone runs Android version Android 14.
    Android 7 Nougat vs Android 14
  • No location privacy controls
    This smartphone does not offer location privacy controls, the average smartphone does. 88% of smartphones include location privacy features.
  • Lacks app tracking protection
    This smartphone does not have app tracking protection, the average smartphone does. 70.2% of smartphones include app tracking protection.
  • Lacks focus mode
    This smartphone does not have a focus mode, the average smartphone does. 60.4% of smartphones include a dedicated focus mode.
  • No camera/mic privacy toggles
    This smartphone lacks camera and microphone privacy toggles, the average smartphone includes them. 87% of smartphones offer these toggles.
  • No Wi-Fi password sharing
    This smartphone does not support Wi-Fi password sharing, the average smartphone does. 57.9% of smartphones allow easy Wi-Fi sharing.
  • No notification customization
    This smartphone does not allow notification customization, the average smartphone does. 99.1% of smartphones offer advanced notification options.
  • No battery health monitoring
    This smartphone lacks battery health monitoring, the average smartphone includes it. 66.3% of smartphones provide battery health stats.
  • Lacks dark mode
    This smartphone does not support dark mode, the average smartphone does. 95.8% of smartphones have dark mode.
  • Does not allow app offloading
    This smartphone does not support app offloading, the average smartphone does. 51.9% of smartphones support app offloading to save space.
  • Lacks instant markup
    This smartphone does not support instant markup, the average smartphone does. 52.2% of smartphones include instant markup tools.
  • No scrolling screenshot support
    This smartphone does not support scrolling screenshots, the average smartphone does. 81.1% of smartphones allow scrolling screenshots.
  • No theme customization
    This smartphone does not support theme customization, the average smartphone does. 91% of smartphones allow theme customization.
  • No offline voice commands
    This smartphone does not support offline voice commands, the average smartphone does. 90.4% of smartphones offer offline voice control.
  • No picture-in-picture mode
    This smartphone does not support Picture-in-Picture (PiP), the average smartphone does. 97.9% of smartphones offer PiP mode.
  • Does not allow play while downloading
    This smartphone cannot play games while downloading, the average smartphone can. 77.3% of smartphones support play-while-downloading.
  • No dynamic theme support
    This smartphone does not support dynamic themes, the average smartphone does. 81.9% of smartphones support dynamic theming.
  • Lacks extra dim mode
    This smartphone does not have extra dim mode, the average smartphone does. 82.5% of smartphones offer extra dimming features.
  • Lower-resolution main camera
    This smartphone has a lower-resolution main camera than the average smartphone (16 MP & 12 MP vs 50 MP & 8 MP). The average smartphone has a 50 MP & 8 MP main camera.
    16 MP & 12 MP vs 50 MP & 8 MP
  • Lower front camera megapixels
    This smartphone has lower front camera megapixels than the average smartphone (8 MP vs 16 MP). The average smartphone has a 16 MP front camera.
    8 MP vs 16 MP
  • No timelapse video
    This smartphone does not support timelapse video, the average smartphone does. 92.3% of smartphones include timelapse modes.
  • No continuous autofocus in video
    This smartphone does not support continuous autofocus in video, the average smartphone does. 94.2% of smartphones have continuous AF.
  • No burst mode
    This smartphone does not have a burst mode, the average smartphone does. 98.1% of smartphones support burst shooting.
  • 1.9% smaller main camera sensor area
    This smartphone has a smaller main camera sensor area than the average smartphone (31.4 mm² vs 32 mm²). The average smartphone sensor area is 32 mm².
    31.4 mm² vs 32 mm²
  • No 5G connectivity
    This smartphone does not support 5G connectivity, the average smartphone does. 66.9% of smartphones are 5G compatible.
  • Older Bluetooth version
    This smartphone uses an older Bluetooth version than the average smartphone (5 vs 5.2). The average smartphone uses Bluetooth 5.2.
    5 vs 5.2
  • 50% lower refresh rate
    This smartphone has a lower refresh rate than the average smartphone (60 Hz vs 120 Hz). The average smartphone has a refresh rate of 120 Hz.
    60 Hz vs 120 Hz
  • 1.17 inches inch smaller screen size
    This smartphone has a smaller screen size than the average smartphone (5.5 inches vs 6.67 inches). The average smartphone has a screen size of 6.67 inches.
    5.5 inches vs 6.67 inches
  • 52.4% lower screen brightness
    This smartphone has a lower screen brightness than the average smartphone (314 nits vs 660 nits). The average smartphone has a brightness of 660 nits.
    314 nits vs 660 nits
  • Lower screen resolution
    This smartphone has a lower screen resolution than the average smartphone (1080x1920 px vs 1080x2400 px). The average smartphone has a resolution of 1080x2400 px.
    1080x1920 px vs 1080x2400 px
  • 28% smaller battery capacity
    This smartphone has a smaller battery capacity than the average smartphone (3,600 mAh vs 5,000 mAh). The average smartphone has a capacity of 5,000 mAh.
    3,600 mAh vs 5,000 mAh
  • 45.5% slower charging speed
    This smartphone has a slower charging speed than the average smartphone (18 W vs 33 W). The average smartphone charges at 33 W.
    18 W vs 33 W
  • No LDAC support
    This smartphone does not support LDAC, the average smartphone does. 60.3% of smartphones support LDAC.
  • No aptX HD
    This smartphone does not support aptX HD, the average smartphone does. 50.7% of smartphones support aptX HD.
  • 7 year/s older release date
    This smartphone is an older model than the average smartphone (2017 vs 2024). 7.00% of smartphones were released more recently.
    October 2017
    2017 vs 2024
  • Poor brand origin
    This smartphone has a poorer brand origin compared to the average smartphone. 0.00% of smartphones come from top-tier brand origins.
    Taiwan vs China

Video reviews

Hands-on testing, unboxing, and real-world video evaluations

6.0
PhoneArena
≈ estimated
20/12/2017
Hands-on review · camera, battery and performance tests
Verdict
Asus Zenfone 4 Pro ZS551KL is solid and fast, but its camera cannot beat the cheaper sibling, making it a tougher sell.
Hands-on video, no verdict
Overview video
Overview video
Hands-on video, no verdict
Not graded yet
Not graded yet
Not graded yet

Expert reviews

In-depth analysis and verdict from leading tech publications

H
hifitest.de
03/02/2026
Summary of the review
Smartphone Technical Specifications - Asus Zenfone 4 Pro ZS551KL
(Translated)Show original
connect.de
26/03/2018
Lab test · Dual-camera Android
Verdict
The Asus Zenfone 4 Pro is well built with a strong dual camera, but dated bars, weak signal and average battery life hold it back.
X
xataka.com
25/09/2017
Summary of the review
Asus Zenfone 4 and Zenfone 4 Pro hands-on: pushing dual front and rear cameras to the limit
(Translated)Show original

Third-party reviews

What customers like about Asus Zenfone 4 Pro ZS551KL (6GB + 128GB)

  • Flagship-level performance with Snapdragon 835 SoC and 6GB RAM, handling demanding apps and multitasking smoothly.
  • Excellent battery life that can last a full day or more, even with heavy use.
  • Premium build quality and attractive glass and aluminum design.
  • Vivid and bright AMOLED display, though some found it leaning blueish.
  • ZenUI 4.0 is less bloated than previous versions, offers useful features, and has good customization options.
  • Good connectivity, including a fast and accurate front-mounted fingerprint sensor and a 3.5mm headphone jack.
  • Camera hardware is solid and can produce excellent photos in Pro mode with manual adjustments.
  • Dual-SIM support and expandable storage via microSD card (up to 2TB).
  • Speedy and reliable auto-focus system and optical image stabilization (OIS).

What customers don't like about Asus Zenfone 4 Pro ZS551KL (6GB + 128GB)

  • Camera's automatic mode often produces muted or cold colors and struggles in low light conditions.
  • Poor software support; the phone stopped receiving updates at Android 8.0 Oreo, leading to lack of security patches and potential issues with app performance over time.
  • Sub-par speakers lack mid-range and bass quality.
  • Lack of essential cellular features for some markets (e.g., no VoLTE or Wi-Fi calling support for T-Mobile's network in the US).
  • The glass back is a fingerprint magnet and can be very slick, making it prone to sliding off surfaces.
  • Display maximum brightness is underwhelming compared to other flagship phones, which can affect outdoor visibility.
  • Expensive at launch, making it a tough sell against established competitors like the Samsung Galaxy S8 or LG G6.
  • Some long-term reliability issues reported, such as faulty screen connectors.

Verdict

The Asus Zenfone 4 Pro ZS551KL (6GB + 128GB) is a 2017 flagship smartphone featuring a 5.5-inch Full HD AMOLED display protected by Corning Gorilla Glass 5, powered by the high-end Qualcomm Snapdragon 835 processor and Adreno 540 GPU. Key pros include a versatile dual-camera system with a 12MP main sensor (Sony IMX362, f/1.7, OIS, large 1.4µm pixels) for excellent low-light performance and a 16MP telephoto lens offering 2x optical zoom, as well as Hi-Res audio support with stereo speakers and a 3.5mm jack. The phone has 6GB of RAM, 128GB of internal storage expandable via a hybrid microSD slot, fast charging for its 3600mAh battery, and built-in NFC for mobile payments. Cons are minimal but include the hybrid SIM/microSD slot, which means users must choose between dual SIM functionality or expandable storage, and the phone was released with the older Android 7.1.1 Nougat (upgradable to Android 8 Oreo).

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