I usually watch movies or YouTube videos with my external monitor. But sometimes the video is too dark and turning up the monitor's brightness it's not enough.
You can test it out on https://gdi3d.github.io/change-youtube-videos-brightness/demo.html
It uses the filter properties of CSS and it's applied to the video tag element present on the site.
Yes, but feel free to inspect the code at https://github.com/gdi3d/change-youtube-videos-brightness