The Mac operating system has a little-known feature called Quick Look. Quick Look provides a shortcut for viewing images (and other content) on Macs. You don't need to open Photos or install third-party software to view a thumbnail index or quick slideshow of your images. The information in this article applies to Mac OS 10.8 Mountain Lion and later.
7 Ways to Quickly Preview Image Files on Your Mac
The Quick Search feature lets you view a folder full of images in seconds.
Double-click on a folder of images or use Finder to locate and open the folder of images you want to view. The images can be on any type of media: hard drive, CD, flash drive, or memory card.
Select the images you want to see. If you want the entire folder, use the keyboard shortcut Command+A to select all the files.
