(…not video’s subtitle)

1youtube-dl --o "%(title)s.%(id)s.%(ext)s" $URL;  # first stop
2youtube-dl --sub-lang en --write-auto-sub --sub-format srt --skip-download -o "%(title)s.%(id)s.%(ext)s" $URL;  # and finally
  • if you’re using mpv as video player, use v to display captions.