OS Details

Samsung Galaxy A31 has been launched in March 2020.
Samsung Galaxy A31 have Android 10 , One UI 2.5

Screen Dimensions

Samsung Galaxy A31 screen size is 6.4 inch with ~ 84.9% body ratio of actual device size. Physical dimensions for Samsung Galaxy A31 device is 6.27 x 2.88 x 0.34 INCH or ( 159.3 x 73.1 x 8.6 MM).

Displaying of Units are in this order "Height x Width x Thickness"

Screen Pixel Density and CSS Pixel Ratio

"Pixel" is smallest unit/element of any display.

The total number of pixels that fit into an inch is referred to as "Screen Density" or "Pixel Density" and it measured as "Pixels Per Inch".
Pixel Desnsity have limits to display Pixels Per Inch depends on different screen sizes. When number of pixels per inch increases than it's screen-size limit, the Display resolution will increase but actual device width/height in pixels remain same. Actual device pixels are known as Device Independent Pixels or CSS Pixel Ratio.

Samsung Galaxy A31 resolution is 1080 x 2400 ^PX with ~ 411 pixel desnsity.
Samsung Galaxy A31 viewport size is 412 x 915 ^PX with ~ 157 actual pixel density, which means it have 2.625 xxhdpi display pixel density.

Screen Resolution and Viewport

The sum of pixels which are displaying on a device is called as "Screen Resolution". and sum of actual pixels of any device is reffered to as "Viewport".

Samsung Galaxy A31 have 6.4" physical screen size and its resolution is about 1080 x 2400 Pixels with approximately 411 PPI pixel density. Samsung Galaxy A31 has viewport size 412 x 915 Pixels and its pixel ratio is about 2.625.

For better understanding screen actual sizes, viewport sizes, display resolution and about their density click here.

CSS Media Queries

Samsung Galaxy A31 css media queries will help developers to write styles specifically for Samsung Galaxy A31. Here are details:

Samsung Galaxy A31 Media Queries (In terms of Mobile only)

@media only screen and (min-width: 412px) and (max-width: 767px) { /* Your Styles... */ }

Samsung Galaxy A31 Min-Width Media Queries

@media only screen and (min-width: 412px) { /* Your Styles... */ }

Samsung Galaxy A31 Min-Height Media Queries

@media only screen and (min-height: 915px) { /* Your Styles... */ }

Samsung Galaxy A31 Landscape Media Queries

@media only screen and (min-width: 915px) and (orientation: landscape) { /* Your Styles... */ }

Samsung Galaxy A31 Portrait Media Queries

@media only screen and (min-width: 412px) and (orientation: portrait) { /* Your Styles... */ }

Samsung Galaxy A31 Device Width Media Queries

@media only screen and (min-device-width: 412px) and (orientation: portrait) { /* Your Styles... */ }
@media only screen and (min-device-width: 915px) and (orientation: landscape) { /* Your Styles... */ }

Samsung Galaxy A31 Retina Media Queries

@media
  only screen and (-webkit-min-device-pixel-ratio: 2.625),
  only screen and (   min--moz-device-pixel-ratio: 2.625),
  only screen and (     -o-min-device-pixel-ratio: 2.625/1),
  only screen and (        min-device-pixel-ratio: 2.625),
  only screen and (                min-resolution: 411dpi),
  only screen and (                min-resolution: 2.625dppx) { 
    /* Retina styles here */
}
                                

Retina is actually based upon device pixel ratio. Devices mostly have 2x or 3x display so you can use general retina media queries to display high resolution content on all kind of devices. Retina 2x and Retina 3x media queries given below:

Retina 2x Media Query (for all 2x resolution supported devices)

@media
  only screen and (-webkit-min-device-pixel-ratio: 2),
  only screen and (   min--moz-device-pixel-ratio: 2),
  only screen and (     -o-min-device-pixel-ratio: 2/1),
  only screen and (        min-device-pixel-ratio: 2),
  only screen and (                min-resolution: 192dpi),
  only screen and (                min-resolution: 2dppx) { 
    /* Retina styles here */
}
                                

Retina 3x Media Query (for all 3x resolution supported devices)

@media
  only screen and (-webkit-min-device-pixel-ratio: 3),
  only screen and (   min--moz-device-pixel-ratio: 3),
  only screen and (     -o-min-device-pixel-ratio: 3/1),
  only screen and (        min-device-pixel-ratio: 3),
  only screen and (                min-resolution: 384dpi),
  only screen and (                min-resolution: 3dppx) { 
    /* Retina styles here */
}
                                

Samsung Galaxy A31 Specifications

• Launch Date March 2020
• Android 10
• Physical Screen Size 6.4 INCH
• Resolution 1080 x 2400 PX
• Viewport Size 412 x 915 PX
• Pixel Density 411 PPI
• Device-Independent Pixels 157 PPI
• Pixel Ratio 2.625 xxhdpi
• Width 1080 PX
• Height 2400 PX
• Device Width 412 PX
• Device Height 915 PX
• Dimensions 159.3 x 73.1 x 8.6 mm (6.27 x 2.88 x 0.34 in)
• Weight 185 g - 7.34 oz