Here is a list of options for “target-densityDpi”.

device-dpi: Use the device’s native dpi as target dpi.
low-dpi: 120dpi
medium-dpi: 160dpi, which is also the default as of today
high-dpi: 240dpi : We take any number between 70 and 400 as a valid target dpi

<meta name="viewport"
      content="
          height = [pixel_value | device-height] ,
          width = [pixel_value | device-width ] ,
          initial-scale = float_value ,
          minimum-scale = float_value ,
          maximum-scale = float_value ,
          user-scalable = [yes | no] ,
          target-densitydpi = [dpi_value | device-dpi |
                               high-dpi | medium-dpi | low-dpi]
          " />

For Example

<meta name=”viewport” content=”user-scalable=no, initial-scale=1, maximum-scale=1, minimum-scale=1, width=device-width, height=device-height, target-densitydpi=medium-dpi” />