You can easily get to know about the likes and dislikes of any video before playing it. Ratings Preview for YouTube™ is a Google Chrome extension that displays a likes and dislikes bar showing ratings of videos on YouTube.
The bar is shown on every YouTube video thumbnail which simply helps you to get an idea of the overall rating given to individual videos.
The red color in bar represents dislikes whereas the green color shows likes. So longer the red bar is, the more bad ratings made on that video.
When Video Ratings Are Disabled By The Owner? If the owner of any video has disabled ratings, the extension will display a grey color bar.
The extension can also be set to auto-highlight best videos on YouTube pages like search and related videos section, highlighted videos get enclosed in a blue box.