In the Mac Finder, various key combinations let you perform operations that would normally require a mouse, trackpad or other input device. The Option (or Alt) ⌥ key lets you access many hidden options, not only in the Finder but in many other places too. It is so important that someone has even written an entire book dedicated to the “magic” of the Alt key (in French, here as a PDF). Below are some useful combinations that are probably little known even among more experienced users.
Quickly get details with System Information
Hold down the Option key, click the Apple menu and choose “System Information”: you can instantly open the System Information section with all the details about your computer
Quickly close folders when opening subfolders
Double-click a folder in the Finder while holding down Option: the folder will open and the previous folder, if any, will close automatically.
Deselect a group of files
You probably all know that to select all the files in a Finder folder you just press Command-A; to deselect all the items, simply press Command-Option-A
Force quit an app
Control-clicking the icon of an open application in the Dock lets you quit it and access other options; if you also hold down the Option key, the “Force Quit” option appears.
Open folders and subfolders in one go
When viewing a folder in the Finder in “as List” mode, you can click the small triangle to the left of a subfolder to show its contents; clicking the triangle while holding down Option opens not only the subfolder but also any subfolders within the selected folder. This shortcut only works in List view.
Skip duplicate files when copying
When you copy a set of files from one location to another in the Finder, it offers to replace or keep both files with the same name. If you also press the Option key while moving them, a “Skip” option appears, letting you continue copying while skipping the individual duplicate file. The “Skip” option is available
Duplicate instead of moving
If, instead of moving a file from one Finder folder to another, you want to duplicate it, simply press Option while dragging. The pointer changes while you drag the item.
Start a full-screen slideshow of the selected files
By selecting a group of files (images, documents) and pressing Option-Command-Y, you can view a Quick Look slideshow of the selected files.
Empty the Trash without the confirmation dialog
Pressing Option-Shift-Command-Delete empties the Trash without displaying the confirmation dialog.
Adjust display brightness in smaller increments
Holding down Option-Shift-Brightness Up or Option-Shift-Brightness Down lets you adjust the display brightness in smaller increments. Adding the Control key to this shortcut lets you adjust the brightness of an external display, if supported.
Enjoy!
