Maximise a window on Mac without going into fullscreen mode
With OS X Yosemite Apple changed the default behaviour of the green maximise button. Instead of simply expanding the current window it now launches into Fullscreen mode. There are, however, ways to revert back to the old maximise function - albeit temporarily.
Prior to Yosemite, fullscreen mode was activated by clicking a dedicated fullscreen button that appeared in the top right corner of applications windows. The red, yellow and green "traffic light" buttons in the top left retained their traditional functions of closing, minimising and maximising the window respectively.
With Yosemite the fullscreen button was removed and the green traffic light button inherited its function, leaving no obvious way to simply maximise a window without also entering fullscreen mode.
How to maximise a window without going fullscreen
Fortunately the old-school maximise function is still available, the methods to use it are just a little more obscure than they were before.
Method 1 - Hold alt while hovering over fullscreen button
If you'd like to simply maximise a window without entering fullscreen mode, hover the green fullscreen button and hold down the
You should see the icon on the button change from the fullscreen logo to the old maximise + icon. Click the button with alt still held down, and the window should maximise just like it would have done if you were using any OS X version prior to Yosemite.
Method 2 - Double-click the title bar
Another less well known method of maximising the window rather than going fullscreen is to double-click on the grey title bar.
Note: for some users, this may minimise the window instead. If thats the case for you, head into System Preferences -> Dock and then change the selection in the dropdown box next to Double-click a window's title bar to from minimise to zoom (and ensure that the option is ticked) as shown below.