It used to be that if you wanted to zoom any window on your Mac to see as much of the content inside it as possible, you’d hit OS X’s green button in the upper left of the window.
As of OS X Yosemite, the green button turned into a “full screen” trigger, zooming any window out to completely fill your Mac’s monitor.
If you hate that behavior, here’s an easy way to get the original zoom feature without the full screen.
There are two ways to expand any window on your Mac. One trick, which came around when OS X Yosemite did, is to Option-Click the green button itself. That’s all well and good, but it does require a little extra thinking, and if you accidentally hit the green button without the Option key, you’ll get a full screen window. Not good.
The best way, in my opinion, to zoom your windows out to fit the size of the content within them is to double click on the title bar.

Photo: Rob LeFebvre/Cult of Mac
This should come enabled by default, but if it’s not working for you, head into your System Preferences app and open up the Dock preference pane. Once there, make sure that the checkbox next to “Double-click a window’s title bar to…” is checked and that zoom is selected in the drop-down menu (instead of minimize).

Photo: Rob LeFebvre/Cult of Mac
If you do that, now you can have a host of options when dealing with El Capitan windows – red button to close, yellow button to minimize, green button to make it full screen, and a double-click on the title bar to maximize to fit the content.
How great is that?
Via: WonderHowTo
5 responses to “How to maximize your El Capitan windows without going full screen”
Not so great. The zoom doesn’t always maximize to 100% of the screen. Tested on Safari and few other apps. Instead of this, I’ve been using third-party apps like Cinch for the past 7 years. Works great.
Yes, not much useful, for e.g. I am web developer, so if I open some older website that are narrow, the method doesn’t work, it work for your site though.
The title should be “How to Zoom your El Capitan window”, not maximize. Double clicking the title bar (or Opt/Alt+Click the green button) = Zoom, not Maximize, which makes the window as big as it needs to be, not necessarily maximized. I like Zoom because it let’s me see the edges of my desktop & other windows, but for those who come from Windows or just prefer Maximized windows, it might be more helpful if the green button WAS maximize instead of Full Screen (especially while using dual monitors). I very rarely put anything in Full Screen; I’m almost always working on more than one window at a time.
There are even easier ways, albeit using third-party apps. One is Magnet, which probably has the smallest memory footprint but can be a bit fussy if you move an app from one screen to another (i.e. if you’re using multiple screens); however, it works fine. Another is BetterSnapTool, which is rock-solid. Both of them also allow you to “snap” windows to left- or right-hand edge of the screen, or to the four corners. Neither is expensive.
Or you can just install BetterTouchTool and enable its Window snapping capabilities…