"Turn Off the Lights" extension (although it's available for other browsers as well). Once installed, the Turn Off the Lights icon -- which is a light bulb -- appears in the right side of your URL bar in Chrome (right next to the star or bookmark icon). When you go to a YouTube window or an article with a video on a news site, you can click on the light bulb icon and it will darken everything on the screen except the clip, effectively hiding distracting or questionable content.
|Before Turn Off the Lights is enabled|
|After Turn Off the Lights is enabled|
There are other tools that accomplish similar effects with video, but Turn Off the Lights is easy to use and has solid customization choices. If you show videos to audiences and would like to focus their attention on the actual clip, it's a great option.