How to Close all the Open Windows at Once on the Mac
As you continue to open multiple windows on your Mac, you may begin to lose visibility of important windows or files. Although the Spaces applications can help you sort your application windows by separating them into different screens, you can also simply close out all of your windows and start fresh. Be sure to save any document or email you are currently using before closing out, as you may lose your unsaved work.
Save your work. Click "File" at the top of the screen and select "Save" from the drop-down menu.
Close email drafts. Click the "Save as Draft" button the "New Message" window in Apple Mail.
Press and release "Option," "Command" and "W" key simultaneously. This closes all of the open windows in the application you are currently using.
Press and release "Command" and "Q."
Click the "Apple" icon at the top of the screen, and click "Force Quit" from the drop-down menu. Click the application you wish to close, and click the "Force Quit" button. This should be used only if the application becomes unresponsive.