It can be advantageous to preview files before opening them and can save a lot of time. For instance, if you have a few documents open, you might want to preview them instead of checking each separately to find the one you’re looking for. macOS does not have the native capability to preview open apps or windows. To obtain this functionality on your Mac, you can use third-party apps like HyperDock, uBar, and ActiveDock which allow you to preview a file by hovering over it.