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I have a iMac (27-inch, Late 2009) running OS X Yosemite v 10.10.2. Mysteriously, a rectangle has appeared in the middle of the screen.

Proportionately, it looks like a golden section. It floats on top of everything else.

enter image description here

Close up:

enter image description here

Almost like a ghost of something, but I don't remember opening anything that size.

Any ideas about this?

Could someone/something have hacked my machine?

How do I get rid of it?

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  • Do you see any suspicious-looking processes in Activity Monitor?
    – user24601
    Commented Feb 18, 2015 at 0:00
  • @user24601 - I looked, but didn't see anything unusual. Nothing else seems affected. It just gives the feeling of the monolith appearing in 2001 A Space Odyssey, just mysteriously hovering in the sky. I can always try rebooting the machine, but I'd really like an explanation for this thing first.
    – Jagra
    Commented Feb 18, 2015 at 0:39
  • Hmm... what happens to the mysterious hovering thing if you change your display's resolution?
    – user24601
    Commented Feb 18, 2015 at 0:40
  • it is still there after restart, or in Safe mode, or another user ? it looks like a app is placing it there.
    – Ruskes
    Commented Feb 18, 2015 at 0:41
  • @user24601, I changed resolution and it moved around like any other window.
    – Jagra
    Commented Feb 18, 2015 at 0:44

4 Answers 4

Reset to default
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Steps to evaluate where it comes from.

  1. Switch User to see if it is user specific

  2. Restore Disk permissions.

  3. Start in Safe mode to eliminate 3d party applications

  4. It looks like it is a left over from some app that did not close properly, next time if it happens remember what app you just closed.

If problem persists, use Apple Hardware Test.

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A floating black rectangle appeared on my Mac screen after upgrade to High Sierra operating system. It is due to an Accessibility option and can be removed as follows:

System Preferences > Accessibility > Zoom > Options > Show preview rectangle when zoomed out

I do not know how it appeared, but I am glad that it is gone.

Screenshot of System Preferences option mentioned

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I landed here looking for an answer and I ended up finding one myself. I had the same problem. I just used Command + Option + Escape to launch Force Quit, selected Finder and clicked on Relaunch. The rectangle disappeared and I could carry on with my life. :)

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Does this occur at all times, even after restarts and for other users, too?

To test, please logout and then login to the account on which this artifact appears.

Alternatively, restart the Mac; or shutdown and boot it up. All too often, small artifacts like this persist only in the current login session and will disappear when the user logs in again, or the machine is given a restart.

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