Force Dock to hide programs on switch Manhattan KS

But what if you'd like to always use this mode, without the need to hold down the Command and Option keys? With a little help from Terminal, you can easily make the Dock do just that. Open Terminal (in Applications -> Utilities), and enter these two commands (don't type the $ symbol; those are just new line symbols):

$ defaults write com.apple.dock single-app -bool TRUE$ killall Dock

When the Dock restarts, any time you click a program's icon in the Dock, all other open programs will hide. Note that this behavior is all-or-nothing; you can't selectively decide which apps hide and which apps don't hide. It will, however, only work if you click the Dock; clicking a program's window in the Finder, or using Command-Tab, will not invoke the "hide all" behavior. If you decide that this always-hiding approach isn't ideal, you can reverse it with these commands:

$ defaults delete com.apple.dock single-app$ killall Dock

As an alternative solution to the "I need to focus on this app" problem, you might try Freeverse's free Think. While not an exact replacement for "hide others on switch," it has some nice features that make it easier to focus on one program at a time.