The Green Button Gamble
In macOS, window management differs significantly from Windows. The green button in the top-left corner of a window (next to the red close and yellow minimize buttons) does not traditionally “maximize” a window to fill the screen while keeping the menu bar visible. By default, clicking the green button puts the application into a dedicated “Full Screen” mode, hiding the Dock and menu bar, and creating a new desktop Space. Furthermore, if you hold the Option key and click it, or double-click the title bar, macOS performs a “Zoom.” Instead of filling the screen, Zoom automatically changes the window size to whatever dimensions the operating system thinks are best to display the current content, which often results in a narrow, unpredictable window shape.
Disabling Automatic Zooming
To maintain consistent window dimensions and stop macOS from automatically changing window sizes unpredictably when you interact with the title bar, you can change the default behavior of the double-click action.
Open System Settings (click the Apple logo in the top-left corner). In the left-hand sidebar, scroll down and click on Desktop & Dock. Look at the main window on the right and scroll down to the “Windows” section. Locate the option labeled Double-click a window’s title bar to. By default, this dropdown menu is set to “zoom.” Click the dropdown menu and change the selection to minimize, or select Do Nothing if that option is available in your version of macOS. Now, double-clicking the title bar will predictably minimize the window to the Dock (or do nothing) rather than triggering the erratic auto-resizing Zoom function. (Note: The green button will still trigger Full Screen unless you hold Option to override it).