How can I permanently modify OS X's green window button?

Question

In older versions of Mac OS X, clicking the green button in a window title bar cause the window to grow in size, usually to grow to the full height and/or width of the screen.

In later versions, the behavior changed. Now clicking the green button causes the window to enter full-screen mode with both the menu bar and Dock hidden. Holding down the Option key while clicking the green button provides the grow-window behavior while changing the icon displayed when hovering.

I would like to revert to the old behavior where clicking the green button grows the window without going into full-screen mode.

Is there a way to permanently modify the behaviour of the green window button in OS X 10.11 (El Capitan)? Or more recent versions?

Perhaps some preference setting written with at command-line tool in Terminal.app?

Might be nice to reverse the behaviors, if possible:

• Click to grow window
• Option+click to enter full-screen mode.

The following approaches are not suitable solutions:

• Option+click
• Any app that provides a hotkey or drag options
• Spectacle
• BetterTouchTool
• Double-click the title bar

Answer 1

The behaviour you want to achieve is not trivially possible on OS X. The behaviour requires modifications to the underlying window management framework.

Individual application developers may be able to achieve this behaviour but this would go counter to Apple's Human Interface Guidelines. Going against these guidelines might risk the application being rejected from the Mac App Store.

Tell Apple

Send Apple your feedback and let them know what you want and, most importantly, why you want this behaviour.

Answer 2

rightzoom.app does exactly and just this. I used it under Yosemite, but not yet under Big Sur on M1