Install mps-youtube for viewing Youtube videos from terminal:
sudo pacman -Syu mps-youtube
If you have mpv installed, it will run videos in mpv.
Run mps-youtube with:
mpsyt
By default, mps searches and plays only music. To change this type following commands:
set search_music false
set show_video true
To search type:
/ [SEARCH TERMS]
To play a video, just type in the number in front of it in the playlist.