YouTube has a dark theme which can change the white background of the page into the dark in your browser. The dark theme gives you the cinematic experience and reduces eye strain at night.
NOTE: Make sure that you are using the new YouTube site and have installed the latest browser on your computer. All latest versions of Chrome, Firefox, Opera, and Edge supports dark theme in Windows.
How To Activate Dark Theme on YouTube
1: Load YouTube
Open the web browser on your computer and load YouTube by typing youtube.com in the browser's address bar.
2: Access the "Dark theme Off" menu
Click on "Settings" icon (three vertical dots) which you can see before "SIGN IN" option. Doing this will enable the drop-down menu having "Dark theme Off:" option. If you have already signed in, then you can get this option by clicking on your profile icon in the top right corner.
3: Dark theme toggle switch
Select the "Dark theme Off:" option from the drop-down menu. After doing this you will see the "Dark theme" box from where you can activate the dark theme. Now activate the dark theme by sliding the toggle switch on, which you can see in the bottom right corner of the box.
How To Deactivate Dark Theme on YouTube
To switch back to the default theme, re-access the setting or profile icon. Select "Dark theme on" option from the menu and deactivate the dark theme by sliding off the toggle switch.
Watch this video tutorial to learn more about on "How To Activate or Deactivate Dark Theme on YouTube Desktop Site."