View and edit files with Quick Look on Mac
Quick Look offers a fast, full-size preview of nearly any kind of file without opening the file. Just press the Space bar to rotate photos, trim audio and video clips, and use Markup to crop photos and annotate images or PDFs. You can use Quick Look for items in Finder windows, on your desktop, in emails and messages, and other places.
On your Mac in a Finder window or on the desktop, select one or more items, then press the Space bar.
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:
Resize the window: Drag the corners of the window.
You can also use Quick Look full screen. Click the Full Screen button
in the Quick Look window. To stop using it full screen, move the pointer to the bottom of the window, then click the Exit Full Screen button 
that appears.Browse items (if you selected multiple items): Click the arrows near the top-left of the window or press the Left Arrow and Right Arrow keys. In full screen, click the Play button
to view the items as a slide show.Show items in a grid (if you selected multiple items): Click the Index Sheet button
or press Command-Return.Zoom in and out of an item: Press Command-Plus (+) to make the image bigger or Command-Minus (–) to make it smaller.
Rotate an item: Click the Rotate Left
button or press and hold the Option key, then click the Rotate Right 
button. Keep clicking to continue rotating the item. Mark up an item: Click the Markup button
. See Mark-up files.Trim an audio or video item: Click the Trim button
, then drag the yellow handles in the trimming bar. To test your changes, click Play. You can start over by clicking Revert. When you’re ready to save your changes, click Done, then choose to replace the original file or create a new one.Open an item: Click Open with [App].
Share an item: Click the Share button
.
When you’re done, press the Space bar or click the Close button
to close the Quick Look window.
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.