Among some of the seemingly smaller changes made in newer versions of Mac OS from OS X Yosemite onward is an adjustment to how a windows green Maximize button behaves.
In older versions of Mac OS X, clicking on the green maximize button would expand and enlarge the window to a larger size, but in the newest macOS releases, clicking on the green maximize window sends the window (or app) into Full Screen mode.
If you prefer the older maximize button behavior and would rather windows become larger instead of being sent into full screen, you can modify the maximize behavior with a simple keypress, or by using a new double-click trick.
How to Make the Green Maximize Window Button Zoom Windows in Mac OS X
To change the maximize behavior, simply hold down the OPTION button as you hover your mouse cursor over the green zoom button.
You’ll notice that the button changes from two arrows moving in opposite directions indicating expansion into full screen mode, into a (+) plus icon, indicating the buttons behavior has changed. Using the Option+click will result in a larger window rather than a full screen window.
There is probably a way to permanently switch the Option+Click behavior to become the standard behavior using a defaults write command string, but thus far it has yet to be discovered. If you happen to figure it out, be sure to let us know in the comments!
How to Maximize Windows with a Double-Click in Mac OS X
Another way to maximize windows in Mac OS X now without making them full screen is to simply double-click the window titlebar, this instantly enlarges the window in the same way that option-clicking the green maximize button does, zooming in without going full screen.
Longtime Mac users may remember that double-clicking the titlebar has served other functions before, ranging from window shading to minimizing, but now in the most modern MacAOS and Mac OS X versions, it enlarges and zooms a window instead.
Finally, another option would be to set up a specific keyboard shortcut for maximizing windows, a trick that’s not specific to the latest versions of Mac OS X and works on prior releases as well. Go here to learn how to do that amongst a variety of other window management tricks for Mac OS X.