Dot per Inch (dpi)
Dot per inch (DPI) counts how many ink dots fit along one inch — the standard print resolution unit for printers and scanners.
DPI appears on printer specs, photo print settings, and prepress workflows where physical ink dots define output sharpness.
Pixel per Inch (ppi)
Pixel per inch (PPI) counts screen or image pixels along one inch. Numerically it equals dot per inch here, but PPI refers to pixels in a digital image rather than physical ink dots.
PPI describes monitor density, retina displays, and export settings for web and mobile graphics where pixels — not ink — define resolution.