user6523: Is it smart to watch a 4k video on a 1080p monitor versus watching it in 1080p (especially on youtube)? Is there any difference for the human eye?

user6671: Others have said the answer is simply no, but that's not entirely true. You can get some slight improvement from downscaling; errors and artifacts in the stream will be less visible, but this slight improvement usually isn't worth the increased bandwidth usage and CPU usage.  Effective downscaling also requires graphics which can manage it, Nvidia GTX GPUs can do this, I'm not sure about AMD or Intel graphics.

user6207: There's not a lot of point to it. You're using more network bandwidth to download it, and your computer is working harder to display it, but no, you get no additional visible quality from it. In fact, it's likely that you'll get lower quality because the computer has to downsample it before it can display it.

user2836: No, there is no difference to the human eye (or exceptionally minimal).  Your monitor can't display higher quality than it is capable of displaying.  The only advantage you would have is if you were to zoom in on part of the image, you would have more detail when you zoomed in.
The exception to this is if the 4k stream uses enough extra bandwidth to reduce the number of artifacts present in the stream, but for a well configured stream this shouldn't be a significant factor.  For Youtube settings, that may or may not be noticeable depending on your sensitivity to artifacts and the type of content you are viewing.

6523: <p>Is it smart to watch a 4k video on a 1080p monitor versus watching it in 1080p (especially on youtube)? Is there any difference for the human eye?</p>
 6671: <p>Others have said the answer is simply no, but that's not entirely true. You can get some slight improvement from downscaling; errors and artifacts in the stream will be less visible, but this slight improvement usually isn't worth the increased bandwidth usage and CPU usage.  Effective downscaling also requires graphics which can manage it, Nvidia GTX GPUs can do this, I'm not sure about AMD or Intel graphics.</p>
 6207: <p>There's not a lot of point to it. You're using more network bandwidth to download it, and your computer is working harder to display it, but no, you get no additional visible quality from it. In fact, it's likely that you'll get lower quality because the computer has to downsample it before it can display it.</p>
 2836: <p>No, there is no difference to the human eye (or exceptionally minimal).  Your monitor can't display higher quality than it is capable of displaying.  The only advantage you would have is if you were to zoom in on part of the image, you would have more detail when you zoomed in.</p>

<p>The exception to this is if the 4k stream uses enough extra bandwidth to reduce the number of artifacts present in the stream, but for a well configured stream this shouldn't be a significant factor.  For Youtube settings, that may or may not be noticeable depending on your sensitivity to artifacts and the type of content you are viewing.</p>
