Here's how it works: it looks for the most interesting rectangle by taking a screenshot of the page and downgrading it. The extension then looks at the colors in the pixelated image to separate the background from the photos. It switches colors to simpler ones until it's basically a bunch of white blocks representing pictures against a blue background. By pinpointing the most prominent rectangle on a web page, the extension increases its chances of finding the object you want to look up.
You'll need to install the social network's Chrome extension to use its enhanced visual search tool. Once you're done, simply right-click on an empty space on a website and click Search. The company says the feature is now out for everyone, but give it a bit of time to make its way to your browser if you can't see the option yet.