PPI
Pixels Per Inch - a unit measuring display pixel density, indicating how many pixels fit within one inch of screen space.
PPI (Pixels Per Inch) measures the number of pixels contained within one inch (2.54cm) of a display, indicating its pixel density. Higher PPI means finer pixels packed more closely together, making text and images appear smoother on screen.
Typical desktop monitors have 72-110 PPI, while smartphones feature high-density displays at 300-500+ PPI. Apple's Retina displays range from approximately 220-460 PPI, a density where individual pixels become indistinguishable to the naked eye.
PPI is often confused with DPI (Dots Per Inch). PPI refers to display pixel density, while DPI refers to printer output density. When creating web images, consider the target device's PPI. For Retina support, provide images at 2x the displayed dimensions. Understanding the relationship between resolution and PPI allows accurate calculation of an image's physical display size.