I know I can open the Screenshot tool by pressing cmd + shift + 4. I can drag the mouse around to specify the area I want to take a screenshot of, but I am wondering how I can keep the width and height ratio 1:1 when moving the mouse cursor.

In image editing software, the combination is usually to hold shift while dragging. On mac using the screenshot tool, this means to lock one of the axis depending on where you start your drag motion. It locks the width if you start dragging up or down, and locks the height if you start dragging left or right.

Pressing alt on the other hand makes the capture area grow in both direction.

holding either cmd or ctrl seems to do nothing.

I really hope there is a key combination to make the width and height scale the same, but I cannot figure out which key combination to use.


My version of macOS is Mojave 10.14.5.

And just to clarify, I want to keep the selection area to grow and remain at 1:1 ratio while actually moving the cursor around, similar to this:

enter image description here

Alternatively resizing the area in equal proportion to each other, meaning the width and the height changes so that the original aspect ratio is intact. The resulting image itself does not have to be 1:1

enter image description here

  • Just checking your actual end requirement - is it that you need the selection area to grow and remain at 1:1 ration while actually moving the cursor around, or is it more that you want to ensure you get a 1:1 ratio screenshot?
    – Monomeeth
    Commented Jun 13, 2019 at 10:29
  • Also, advising the version of macOS you have installed may also be relevant.
    – Monomeeth
    Commented Jun 13, 2019 at 10:30
  • I want it grow and remain at 1:1 while moving the cursor around. I am using Mojave 10.14.5
    – John
    Commented Jun 13, 2019 at 10:40
  • Thanks for the link. I could not find what I was looking for, but found another neat option: To exclude the window's shadow from the screenshot, press and hold the Option (⌥) key while you click.
    – John
    Commented Jun 13, 2019 at 12:55

2 Answers 2


As far as I know the exact thing you are trying to do is not natively possible in the current version of macOS Mojave. The current modifiers that do exist for the screenshot tool are as follows:

  • Holding shift moves only one of the sides of the capture area.
  • Holding option scales up all sides of the capture area from the center.
  • Holding space allows you to move the capture area around.

Alternatively you can use shiftcommand5 which will give you the onscreen capture controls with a few more options for resizing the capture area, however this doesn't include any options for locking the aspect ratio.

  • Thanks for your answer. I could not find any extra options with cmd+shift+5 that can do what I want to do.
    – John
    Commented Jun 13, 2019 at 12:50
  • I guess "not possible" is the correct answer until it is possible.
    – John
    Commented Jun 13, 2019 at 13:36
  • 1
    I downloaded a few of the popular third-party screenshot apps, however none of them had the function that you are needing, so I think that is true for the time being.
    – JnthnWJ
    Commented Jun 13, 2019 at 13:41

While it doesn't appear to be possible to do this while taking a screenshot, here's a simple process to achieve the same result quickly using the built-in Preview app:

  1. 📸 Screenshot the whole screen to the clipboard with ControlCommandShift3
  2. 🚀 Launch the Preview app (CommandSpace to bring up Spotlight, type prev, press Enter.)
  3. ➕ Paste the screenshot into a new Preview window with CommandN
  4. ⬚ Select the square area of the screen you want by holding Shift while dragging the mouse pointer to make a selection. (You can also hold Option to expand the selection from a centre point.)
  5. 🙌 Copy the contents of the selection with CommandC.

💾 Alternatively, if you want the image in a file, at the last step crop the image to the selection using CommandK, then save it.

If you're going to be doing this a lot, you can change your screenshot defaults to always open the image in Preview! Here's how:

  1. Press CommandShift5 to open the settings for screenshots.
  2. In the Options menu, under Save to, click on Preview.
  3. Press Esc

After doing that, screenshotting the whole screen with CommandShift3 (don't need the Control) will do steps 1, 2, and 3 from the above, so you just need to make a selection and copy. 👍🏼

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