In light of all these varying HiDPI display compatibilities, the development of applications and the changes in monitor pixel density have been under great speculation. Until recently most monitors typically had a pixel density* of 96 ppi. Various different company’s monitors were designed to match the display size (inch size) with the resolution, therefore most OS and applications were also made based on this 96 dpi standard. 

However with the advancement of LCD panel technology, products with varying resolutions such as full HD and 4K are appearing on monitors of the same screen dimensions. These include devices with pixel densities higher than 150 ppi, which became particularly common in smartphones and tablets. 

Ever since Vista, Windows has been gradually advancing the HiDPI compatibility of its OS and development platforms (multi-monitor compatibility was introduced from Windows 8.1). However there are still many applications that are not compatible or fully compatible due to the following reasons. In these cases, an application created in the previously standard way will be forcibly enlarged / shrunk by the OS, causing it to become blurry. Furthermore some applications may display without blurring, but the display size will be reduced.

• Depending on the application’s development platform
• HiDPI compatibility may not be facilitated throughout the entire application
• Compatibility is additionally difficult when monitors of varying DPI are used

* What is pixel density (DPI or PPI)?

Pixel density is the specification that defines how detailed a display is. It is expressed in units of DPI (Dots Per Inch) or PPI (Pixels Per Inch). DPI is typically used for OS and applications, and PPI is typically used for LCD panel specs. For example 96dpi means that 96 dots are placed in a 1 inch (2.54 cm) length. The level of detail that you can see on the screen depends on the distance it is viewed from (e.g. viewing a monitor versus a smartphone), so whether or not a certain dpi is high resolution or not depends on the device. However in general the larger the dpi value, the higher the definition.