macOS Sierra: Quick Look files and folders
Use Quick Look to view photos, files, or a folder without opening them. You can use Quick Look for items in Finder windows, on your desktop, in emails, in messages, and other places.
A Quick Look window opens. If you selected multiple items, the first item is shown.
In the Quick Look window, do any of the following:
Manually enlarge the window: Drag its corners.
See the item in full screen: Click the Full Screen button on the left. To return to the previous size, click the Exit Full Screen button .
See the next or previous item: Click the arrows on the left, or press the Left and Right arrow keys. In full screen, you can click Play to view the items as a slideshow.
See the items in an index sheet view: Click the Sheet View button on the left, or press Command-Return.
Play the video portion of a Live Photo: When you open a Live Photo in the Quick Look window, the video portion of the photo plays automatically. To view it again, click Live Photo in the bottom-left corner of the photo.
Open the item: Click Open with [App].
Share the item: Click the Share button on the right.
When you’re done, close the Quick Look window: Press the Space bar, force click again, or click the Close button .