If the current tab is not a Youtube or Udemy video, the extension icon will appear grayed-out and will be disabled. Otherwise, clicking it will display a pop-up with a number, a slider and a button named "reset": - The number displays the current video speed. It will change according to the slider. If you desire a specific speed, you may manually type the number you want. It's maximum precision, however is of 0.1. More decimal numbers will be rounded. - The slider controls the video speed, going from 0.0 to 15.9 - The reset button will set the video speed to 1.0