Creatives are not delivering to HD devices
DFP uses dp (also known as dip), or density-independent pixels, as measurements for ad sizes in the mobile app environment. This means that DFP will treat two devices of the same physical size, but varying screen densities, as the same size. This could cause issues if you’re using a different measure of screen size to traffic creatives to a mobile app.
For example, dpi, or dots per inch, measures how many pixels are in each one-inch span on a device. A device may have measurements of 1920x1080 dpi and 640x380 dp. If you’re using dpi as a measurement of the screen size, it would be easy to assume you could serve a 728x90 large banner to the device. However, because DFP uses density-independent pixels (dp), the size of the screen is taken to be 640x380. Therefore, the 728x90 banner would not serve, and a regular banner size must be used.
Serve high-density creatives to HD devices
With the Google Mobile Ads SDK, you can still cater to devices with higher resolutions by using high-density image creatives. In DFP, you can upload creatives of 1.5x or 2x density in addition to the default of 1x density creatives. When the SDK detects that the device is HD, it will serve the creative with the highest density possible. Learn more.