Since I bought my iMac last year, I have a white pixel on the left of my screen. I'm ok with that, one pixel is not much and I know about dead pixels policies.

My problem is about understanding this "dead" pixel.

But this pixel has a strange behavior. At first, it seems to be always white, but it is actually working ok under certain conditions:

  • the mouse pointer
  • a contextual menu
  • Dock icons
  • a QuickLooks video played in fullscreen
  • other spaces than "1"

The "QuickLooks fullscreen video" and "other spaces" are the one that disturb me the most. In these modes, my pixel is working fine, so it must be a software problem since my pixel is working correctly in those modes.

Any ideas?

  • Thanks for pointing the ambiguity Arjan, I edited my question Nov 10, 2009 at 23:15
  • Then I really think it's not a dead pixel in the screen.
    – Arjan
    Nov 11, 2009 at 0:01

5 Answers 5


but it is actually working ok under certain conditions: [..] other spaces than "1"

If that pixel really works totally as expected in that case, then the screen is fine.

Maybe OS X uses different parts of (video) RAM for different spaces. Maybe playing video or Quick Look uses some specific hardware acceleration functions. (And unlikely, but maybe there's some odd software problem, like a misplaced bit on your harddisk where the Core Graphics framework is located, or some odd software running on your machine.)

Do a hardware test, or take it back to the shop. It's not a dead pixel.

  • I found that the "dead pixel" is only visible when a certain Java application is working. Looks like someone is actually creating a 1x1 window in a strange position on screen... Grrrrr Nov 11, 2009 at 0:33
  • Grrrrr? This is quite a happy ending, though a bit late maybe. :-)
    – Arjan
    Nov 11, 2009 at 7:25
  • Grrrr for bad software that makes the world a worse place than it should be :) Nov 11, 2009 at 11:34
  • But now that you know what caused it, doesn't it feel like you just got yourself a brand new iMac? Maybe put it back into its box to enjoy the unpacking again! ;-)
    – Arjan
    Nov 11, 2009 at 12:06
  • @Vincent, this might be to keep the menu visible. Can you confirm that, when closing all visible application windows, the Java application still gives you a Mac-like menu at the top of the screen? (See also "Creating an offscreen frame in Java" at stackoverflow.com/questions/2186135/… for some technical background.)
    – Arjan
    Feb 2, 2010 at 22:10

Having a dead pixel that gets reactivated sometimes isn't as strange as it seems. There even is software that tries to rapidly switch dead pixels on and off to revive them. Have a look at some dead pixel fix tutorial like this one, there are links to software tools, too.


there's a thread at SU you may find helpful:

What is the best way to fix a stuck pixel on a LCD screen?


I had similar problem on ThinkPad laptop. Turns out that was a bug in Lenovo software that created 1px wide and high window :) Checking it on Windows is simple - cursor changes its shape when pointing at exactly this pixel.


I can pretty much guarantee you that your dead pixel is not a software problem. All the indicators you talk about are not at all impossible; dead pixels are not usually completely dead, but may respond to a variety of changes in color, activity of adjacent pixels, pressure on the substrate, etc etc. Heck, it's even possible that the animation of switching between two spaces could "activate" or "deactivate" the pixel.

Edit: and check out schnaader's recommendations in the other answer; this very volatility means pixels like this might be fixable, at least temporarily.

  • It is still strange that the QuickLooks video going fullscreen fixes the dead pixel while a QuickTime video going fullscreen (same animation) or VLC does not. Reproducible. Nov 9, 2009 at 8:56

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