The Macintosh operating system has a handy feature you can use to preview files and documents before you open them. It’s called “Quick Look” and was introduced into the operating system in Leopard (10.5) in 2007 as a convenient way to evaluate files before you open them.
1. Open a Finder window to the directory where your file is.
2. Click once on the file you want to preview so that it is highlighted in the Finder window, and then hit the spacebar or Cmd-y.
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3. Hit space again to close the quick look window.
4. Highlight a file and click the space bar to get a preview in an “Open File…” dialog.
5. Highlight multiple files and hit the spacebar to preview them. Navigate between them with the right and left arrow keys.
6. Tap the up and down arrow keys to navigate between all the files in a folder