Before OS X Lion, you resized a window by either clicking the green circle in the window’s upper left corner or by dragging the bottom right corner of the window up or down, side to side, or diagonally. These methods worked fine for adjusting the basic size of a window, but most times, it was necessary to combine resizing with moving the window around to get everything just the way you wanted it. Over the years, Apple has made changes to the methods for resizing windows.
With OS X Lion, Apple took the plunge and provided the ability to resize windows on a Mac by dragging any side or corner. This simple change lets you size a window by expanding or decreasing just the side of the window that needs a bit of adjusting. For example, if a window has some content just beyond its right edge, you drag the right side of the window to see the entire content.
Information in this article applies to OS X Lion (10.7) and later.
Resizing a Window
Move your cursor to any side of a window—top, bottom, left, or right. As the cursor nears the edge of the window, it changes to a double-ended arrow. When you see the double-ended arrow, click and drag to resize the window.
Resizing also works on the corners of a window. Move your cursor to any corner to produce the double-ended arrow. Then click and drag. If you hold down the Option key while dragging one of the sides or corners, the window remains centered in its location.
Control Aspect Ratio as You Resize a Window
The Option key isn’t the only key that holds some magic for window resizing; the Shift key does, too. If you hold down the Shift key while you expand or contract a window, the window maintains its original aspect ratio.
Although most windows can be resized, some windows are not resizable.
For example, if the window originally had a 16:9 aspect ratio, and you want to maintain that same ratio of width to height, hold down the Shift key before you drag any of the window’s edges.
Maximizing and Minimizing Windows
To maximize a window until it fills the entire computer screen, click the green button in the top left corner of the window. To return the window to its original size and placement, press the green button again. If you don’t see the buttons in the top left corner, move your cursor to the corner to reveal them.
To minimize a window to the Dock, click the yellow button in the top left corner of the window or click Command + M. To return it to its original size and position, click the thumbnail of the screen on the Dock.
You can also double-click the title bar of a window to either maximize or minimize the window, depending on your settings. Go to System Preferences > Dock and check the box next to Double-click a window’s title bar to. Select either zoom or minimize, depending on how you want the setting to work.
Resizing Split View Windows
OS X El Capitan added a new window type, the split view window. Split View lets you have two full-screen apps open on your Mac while still being able to view both app windows at the same time.
In macOS Catalina, enter Split View by hovering your cursor over the green button in the top left corner of the window and selecting either Tile window to left of screen or Tile window to right of screen. Repeat the process with another app until two apps share the screen in equal spaces side by side.
The options for resizing windows in Split View limited. After you have two windows in Split Screen mode, you can size the windows by moving the bar in the center of the screen to the left or the right. As you make one window narrower, the other window fills the space and become wider.
The process for entering Split View mode varies depending on the Mac operating system.
Resizing Windows in macOS Monterey and Later
Resizing windows gets even easier under certain circumstances if you’re running macOS Monterey (12.0) and later. If you’re using your iPad as a second monitor or another option like a separate screen or a second Mac, windows you move from your main computer will automatically resize to fit the new location. You can still use these other techniques to change the windows after you move them to their new homes, but Apple aims to make them useful immediately with this feature.
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