To read through a book or some other text is called skimming. But all the dictionaries I checked define it as "to read superficially"- so what is the word for casually watching a video without being an involved, thorough viewer, perhaps skipping forward a little at times?
The best word for this is probably skim.
There are certainly dictionary definitions that would seem to allow for this use, e.g.
2 : to read, study, or examine superficially and rapidly
to read or consider something quickly in order to understand the main points, without studying it in detail:
But the more important point is that people appear to use the word this way. Look at these user comments from various on-line discussion forums:
"Sorry I didn't reply earlier when I first read post but then I only skimmed the video"1
"i skimmed the video and dont understand how they got to 11k rpm?" 2
"I have skimmed the video and will come back later and look at the whole thing in detail." 3
"Then I skimmed the video and selected the part that I am interested in and dragged it to the project window" 4
The fact that this specific meaning is not captured by dictionaries is probably because the act of skimming through videos is relatively new.
Another option might be glance over/at/through.
If you glance through or at a newspaper, report, or book, you spend a short time looking at it without reading it very carefully.
This phrase probably has a longer history of being used to refer to the act of looking superficially at something, without necessarily reading it. For instance, you can glance through a stack of photographs. However, to my mind at least, glance does not imply any kind of listening. So if I were glancing at a video, I might be doing it from far away, so that I couldn't hear the sound.