720p (720 lines progressive) is a progressive HD signal format with 720 horizontal lines/1280 columns and an aspect ratio (AR) of 16:9, normally known as widescreen HD (1.78:1). All major HD broadcasting standards (such as SMPTE 292M) include a 720p format, which has a resolution of 1280×720p.

The number 720 stands for the 720 horizontal scan lines of image display resolution (also known as 720 pixels of vertical resolution).^[1] The p stands for progressive scan, i.e. non-interlaced. When broadcast at 60^{[note 1]} frames per second, 720p features the highest temporal resolution possible under the ATSC and DVB standards. The term assumes a widescreen aspect ratio of 16:9, thus implying a resolution of 1280×720 px (0.9 megapixels).

720i (720 lines interlaced) is an erroneous term found in numerous sources and publications. Typically, it is a typographical error in which the author is referring to the 720p HDTV format. However, in some cases it is incorrectly presented as an actual alternative format to 720p.^[3] No proposed or existing broadcast standard permits 720 interlaced lines in a video frame at any frame rate.^[4]

Progressive scanning reduces the need to prevent flicker by anti-aliasing single high contrast horizontal lines.^[5][6] It is also easier to perform high-quality 50<->60 Hz conversion and slow-motion clips with progressive video.