Why on youtube a 1080p video looks better than 720p ? (My screen max resolution is 720p)

A resolution greater than 720p looks better on my 720p screen . I want a clear and basic answere to understand this.

Solution 1:

When a video is uploaded to Youtube, Youtube compress it to make it easier to deliver. Unfortunately, by its nature this compression reduces quality. (By way of example I looked at sizes of a high res video on youtube. The same video encoded at 1080p was 168MB, while only 97.4MB at 720p.

If you have the right tools, you will be able to see that a 1080p video on Youtube is substantially larger then the 720p one. This means that more detail is being provided in the video stream, thus (even though limited by the number of pixels of your display) there is more date, allowing for a better image.

Another probable factor is that your screen is NOT 720p. Most "low res" laptop screens would be 1366x768 - which is bigger then the 1280x720 of 720p. Thus, in full screen mode, your 720p video is being upscaled and loosing quality, while the 1080p video is being downscaled, so can provide more clarity.

Lastly (and I imagine much less likely), its possible that the 720p and 1080p video are encoded with different codecs - with your processor being able to offload processing for the 1080p version but require the CPU to handle the 720p version - and struggling to keep up with it.