Sticker

Sticker offers a simple and intuitive way to manage your windows on a Mac. You need to drag any window to the left edge of your screen to fill the left half of your screen with the window.

You can drag it to the right to fill the right half, and to the top to fill the whole screen with the window. While dragging a window, you can hit any arrow keys to see a shaded area where your window will be resized and repositioned.