You can use two native Mac features to resize windows to half screen or one fourth of the screen.
Mac window resize still sucks. To resize a Finder or app window to exact dimensions, for instance one fourth of the screen, I was using a Magnet app. There are other paid apps you can use as well.
However, if you don’t want to pay for a dedicated app, and you need basic window sizes (full screen, half screen, one fourth), you can use a combination of two options that are built into the Mac system.
2 options to resize a window on a Mac
Hover over the green button and hold the Option key
This opiton will let you:
- Resize the window to half screen and move it to the right side
- Resize the window to half screen and move it to the left side
- Zoom – reduce the window size to skip empty space – it works mainly in folder windows
- Resize the window to fit the screen.
To use this option:
1. Move the cursor over the green button in the top-left corner of the window.
2. Wait until you see a small drop-down menu. If you select any of these options, you will immediately enter the full-screen mode. I hate the full-screen mode, I never use it.
3. Press and hold the Option key to reveal window resize options for regular view, without entering the full-screen mode. When you press the Option key, the icon inside the green dot turns into “+”.

To reduce the window to 1/2 screen and move it to the right ▸ Hover over the green button, hold the Option key, and select “Move Window to Right Side of Screen.”
To reduce the window to 1/2 screen and move it to the left ▸ Hover over the green button, hold the Option key, and select “Move Window to Left Side of Screen.”
To resize the window to fit the screen ▸ Click the green button while holding the Option key.
Hold the Shift key while resizing the window from the corner
This option lets you resize the window and keep its original aspect ratio.
To use this option:
1. Move the cursor to any of the corners of the window. The cursor should change to arrow. If the window fits the screen, the arrow is facing inward. If the window is smaller, the arrow has two arrowheads.
2. Press and hold the Shift key.
3. Drag the corner to change the window size while keeping original aspect ratio.

How to resize a window to exactly one fourth of the screen
Mac doesn’t have a reliable window snapping system, but we can use the options described above.
We will use Window 1 as a size reference to resize Window 2 to 1/4 of the screen.
1. Go to Window 1, move the cursor over the green dot, hold the Option key and select “Move Window to Left Side of Screen.”
2. Go to Window 2, move the cursor over the top-left corner, hold the Shift key and resize the window to match its left-side edge with the right-side edge of the Window 1.
3. Use Command + ` keyboard shortcut to switch to Window 1, hold the Option key and press the green dot to fit the window to the screen.
4. Press Command + ` to bring Window 2 to the front.
The animation below shows how it’s done. Open it in a new browser tab to see it in full resolution.

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