Images on a display panel are made up of pixels. Resolution represents the number of pixels that a panel can display. A panel that can display more pixels has a higher resolution and can present a sharper image.

PPI (Pixels Per Inch) represents the number of pixels per square inch. Higher PPI means the more details a panel displays. For the same given screen dimensions, higher resolution also means higher PPI.

UHD 4K ultra high resolution technology has now become the mainstream trend for displays . It is used in LCD TVs, public information displays, desktop monitors, notebook PCs and smartphones. UHD 4K has a resolution of 3840 x 2160 pixels, meaning the display panel or displayed content has a horizontal resolution of 3840 pixels and a vertical resolution of 2160 pixels. This is double the vertical and horizontal resolution of HD (1920 x 1080). As UHD 4K has 4-times the number of pixels as full HD, it can represent much clearer and more detailed images. In addition to the enhancement of fine details and sharpness, it also presents clearer image depth for more stereoscopic pictures. It not only provides more details with more vivid colors as well as a greater sense of space and depth on static contents, but also enables smooth motion. When incorporating with wide color gamut technology, it results in more vivid and life-like colors.

Nowadays consumers read, transmit and share large amounts of images and videos on personal mobile devices. It creates higher demands for screens showing finer details Mobile devices such as smartphones, notebook PCs and wearable displays are viewed at a shorter range and have higher requirements when it comes to the pixel density in display. PPI is therefore an important measurement of image quality.

The higher the PPI value, the crisper and more details the display will be. High PPI allows for much sharper character display and more complete presentation of web content. . AUO has developed 5.5-inch smartphone panels with over 538 PPI. The sharp and distinct image quality can clearly show all the details of images and the text on web pages without any loss in quality when zooming in or out. Apart from the perfect presentation of image details and depth, it brings images to life when high resolution videos are played.. These all cater to the consumer demand for higher-quality mobile phone displays.