We’ve shown you multiple plugins to make your Quick Look more versatile, but you can do even more. In fact, OS X has a feature built in that is hidden and will make your Quick Look, well, an actual quick look. It’s called XRay Mode, and it allows you to see folder files using Quick Look. Here’s how to get it:
First, open Terminal(Applications > Utilitites > Terminal). Next, copy/paste or type “defaults write com.apple.finder QLEnableXRayFolders 1” (minus the quotation marks) and hit Return. Then, enter “killall Finder” and hit return once more. Open a new Finder window, and press Space while a folder is selected to see its contents.