I purchased a new MacBook Pro 15 (2017) and immediately installed Mojave. I then started to see red pixels appearing on the same line as the top menubar. It happens very rarely, but has already occurred about 4 times per week. Pixels disappear if you move any window. I noticed this while using Firefox and iTerm.

Could it be an issue with hardware (dead pixels) or software (Mojave dark theme)?


  • 1
    Do you see them if you switch to the Light theme?
    – Jesse P.
    Commented Oct 2, 2018 at 12:11
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    I'd switch to Light mode for a week and see if it comes back even once. If not, you could extend your test window to see if it is just more random or consider the mystery solved as being a bug in the Dark theme (the choice would be yours). If it does happen with the Light theme, I'd say it's likely a bad pixel or bad hardware and would suggest a visit to the nearest Apple store for an RMA or repair.
    – Jesse P.
    Commented Oct 2, 2018 at 12:23
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    Same problem here, seeing this also in the dark mode. I noticed it when using the telegram app (MacBook Pro 13 2018)
    – Florian K
    Commented Oct 2, 2018 at 12:30
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    I've been noticing the same thing since upgrading, last 2018 MBP 15in. Mostly seen on Firefox, but also iTerm and Atom (I want to say it was grey on one of those). Seen it on both the top and bottom edge and it tends to blink. The cursor can cover over it, so I don't think it's the monitor. Have you noticed any other graphical glitches? Commented Oct 5, 2018 at 19:43
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    I updated to Mojave yesterday and have exactly the same issue (in Firefox, on the top edge of a tab bar). Seems to be a software glitch, related to graphics/GUI... especially when there is a movie playing.
    – maxx
    Commented Oct 12, 2018 at 20:27

4 Answers 4



This bug is potentially fixed in macOS 11 Big Sur. The bug report I filed is now marked as:

Potential fix identified - In macOS 11

One commenter, Curtis Hard, has stated the issue no longer happens for them with Big Sur.

It's unclear if the fix will be backported to 10.15 or 10.14.

It's definitely not a dead-pixel issue. I've determined it's probably a software bug introduced in Mojave and still present in Catalina. I'm not able to screenshot the glitch in most cases (the glitch will typically immediately disappear), but I have managed to capture it on a couple of videos and screenshots.

The fact that it can be captured in software and the fact that the cursor can cover over the glitched pixels indicates the issue is not in the screen but happening in software.



Here's a screenshot from a screen recording of Firefox, where you can see the grey pixels.

enter image description here

Interestingly, if we zoom in a bit, we can see the pixels are actually outside the window itself.

enter image description here


I've also captured similar glitches happening in Apple's own Finder on regular screenshots.

enter image description here

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Some interesting things to note about it.

  • I've only seen it happen against dark areas of a window.
  • It can happen in both light mode and dark mode (if the window is dark anyway).
  • It mostly happens at the edge of a window (where the shadow is), though I have seen it on the inside of some.
  • It often (but not always) disappears when window focus changes, among other things (window focus changing causes window shadows to change).
    • I've been able to change focus to and from an iTerm window with no shadow (when transparency is enabled), and the glitch outside the bottom edge of the window persisted.
  • It can be captured with QuickTime Player's Screen Recording feature.
  • Mysteriously, though it can be capture with QuickTime, it is invisible to Apple's developer tool Pixie, as seen in this screen recording. Likewise, the Digital Color Meter app does not see it either.
  • I've seen it mostly in grey and red, but also green, yellow, and more colors.
  • The glitch can happen even when Finder is not running, so it's not a part of Finder.
  • Running killall Dock while SSH'd into a machine displaying the glitch may cause it to stop, though this may just be a side-effect of shadow changes.
  • I tried suspending all the Firefox processes (firefox + plugin-container processes) over SSH with kill -SIGSTOP while the glitch was happening and the glitch continued to blink, further indicating the glitch is happening outside the Firefox processes.
  • Going further, I tried systematically suspending processes over SSH, to see which one might be responsible. The only one suspending causes the flashing to freeze with was WindowServer.
  • Using the Quartz Debug developer tool (one of the Xcode addition tools, mentioned here), I tested some of the options it had. When the "Disable 2D Acceleration" option was enabled, I was unable to reproduce the glitch like I could when it was disabled. The Autoflush drawing and Vertical Sync options had no effect.
  • It seems to only happen with the integrated graphics card. I have not been able to reproduce it while the discrete card is active.
  • So far I've only heard reports of it happening on recent MacBook Pro and MacBook Air models. I was unable to reproduce this issue on a previous generation MacBook Air running the same OS version.
  • I've not yet seen it happen in a Mojave VM using VMware Fusion, further indicating it only happens with certain hardware.
  • To remove all variables, I tried running a clean install of Mojave 10.14.1 on an external drive. With all default settings, I was quickly able to reproduce it Light Mode with Firefox 63.0.1 with the dark theme and dark developer tools theme enabled and the console open (screen recording).
  • Browser-like applications appear especially likely to trigger it (ie. Firefox and Electron-based apps).
  • Applications I've seen it with (I've probably forgotten some):
    • Firefox (especially versions < 70)
      • Top edge (requires dark Firefox theme)
      • Bottom edge (requires dark bottom of window from open search bar with dark theme, dev tools with dark theme, or dark web page content). Also done on a clean 10.14.1 install.
    • Atom (may require Settings > Core > Title Bar > custom)
      • Top edge
      • Bottom edge
    • Discord
      • Bottom edge
      • Inside window
    • iTerm (with a black, semi-transparent background; it does not seem to happen with an opaque background)
      • Top edge
      • Bottom edge
      • Inside window (at the bottom edge of one pane with split panes)
    • Finder
    • Activity Monitor
      • Top edge
    • Disk Utility
      • Top edge
    • Console
      • Inside window (over the transparent column headers)
    • Mail
      • Inside window (over the transparent column headers)
    • Archive Utility
      • Top edge
    • Hex Fiend
      • Top edge
    • Google Chrome (when using macOS dark mode)
      • Inside window at chrome://downloads/ under light grey horizontal line of top menu bar)
  • I've also seen it happen once at the bottom edge of the drop-down menus from the top menu bar.
  • The selection of apps and places I've seen it with make me suspicious it may in some way be window transparency related.

Things that have no impact on the glitch (tested with Firefox):

  • Doing a clean install of 10.14.1.
  • Resetting PRAM.
  • Resetting SMC.
  • Open the app in low resolution mode.
  • System Preferences:
    • Display resolution scaling.
    • Display color profile.
    • Night Shift.
    • System accent color.
    • Auto-hiding dock.
    • Accessibility > Display > Use grayscale
    • Accessibility > Display > Invert colors


I've only heard claims of it affecting different MacBook Pro models from 2016+ and the 2018+ MacBook Air (the models with USB Type-C). If you are seeing this issue on another Apple computer model, or don't have this issue on one of the affected models, I would be interested to hear about it.


Unfortunately, I don't think there is any way to prevent this glitch at this point, aside from forcing the use of the discrete card if your computer has one (and you don't mind the reduced battery life), but hopefully it will be resolved in a future update.

Even more unfortunate, it still has not been fixed in any version from 10.14.0 through 10.14.6 or the second supplemental update since, and remains unfixed in the first supplemental update for 10.15.7. A comment from Curtis Hard confirms it was still present in the Big Sur betas at the time (it would be great if someone could confirm or deny it exists in newer builds).

I filed a bug report on bugreport.apple.com (not public, but 46079638), which has been marked as a duplicate of 45841204. I don't have access to that bug report, but thought I would mention it in case anyone wants to reference it.

On a side note, there's a good change Apple's future ARM-based computers won't have this issue since they won't have the Intel integrated GPU's. That won't fix the issue for existing Intel computers though.

Firefox 70+:

Since Firefox 70 it doesn't happen as often as it did before, though it still does happen. I suspect this is related to some improvements that reduce the amount of screen drawing.

Steps to reproduce:

I've had the best luck reproducing the bug with Firefox.

  • Open Firefox (63.0.1 in my case)
  • Set Firefox theme to Dark
    • View > Toolbars > Customize... > Themes > Dark
  • Navigate to a page like http://example.com/
  • Open developer tools
    • Tools > Web Developer > Inspector
  • Set developer tools theme to dark
    • In the top right, click ... > Settings > Themes > Dark
  • Click the Inspector tab
  • Open the console
    • In the top right, click ... > Show Split Console
  • Ensure the developer tools covers the bottom of the window
    • If it doesn't, in the top right, click ... > Dock to Bottom
  • Reload the page until the glitch happens


Possibly loosely related: Avoid using a transparent surface by using CoreAnimation (if my suspicion that it is transparency related is correct, that change may eventually have an impact on this bug happening with Firefox, if only by avoiding the OS bug).

Note: If you have any info to share but don't have an account here, you can contact me here.

  • 1
    I have a Macbook Air 2018 running Mojave and this same issue appears (daily for me) between the top edge of Firefox and the bottom edge of the menu bar.
    – mttpgn
    Commented Mar 29, 2019 at 11:11
  • @mttpgn Good to know it also impacts the new MacBook Air. Commented Mar 29, 2019 at 16:14
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    Nice analytical work! On a side note, if you have Firefox installed, it's not a clean install, rather a newly setup system. A clean system has only the default apps, nothing which gets installed after the setup. Very important in some cases, as apps usually change parts of the system (like installing new fonts), which can cause all kinds of bugs to appear which have nothing to do with the OS. Still calling it clean install can lead to frustrations with support if you ever try to go through them... Commented May 15, 2019 at 21:07
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    I joined this community to upvote your answer. I also see this happening multiple times a week. Running a 2018 MBA in dark mode on Mojave 10.14.6 , and FF 68.3.0 esr
    – Luuklag
    Commented Dec 11, 2019 at 15:32
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    I can confirm this is still present in Big Sur (developer here), this happens for me on a Macbook 16" only on the Intel 630 GPU, when switching to 5500M its absolutely fine. I asked a developer at Apple (who worked on the Dark mode and AppKit) who says he was unaware of the issue — I cannot confirm if this is a hardware of software issue (from what I've seen myself and tested it seems software related), it seems to happen what that region of memory/screen needs updating regularly when and blending needs to occur. Commented Jul 7, 2020 at 22:16

This is very much a software issue. It’s reproducable on two different MacBook models running Mojave and two different LG USB-C type displays for me.

Don’t seek hardware repair or reinstall your os if this is your only symptom. Updating software when available is advised since this could be a bug that will get patched.


It's June 30, 2020, and I still see this issue. I have a month-old MacBook Pro 16" running Catalina 10.15.5 with AMD GPU and latest Firefox. Still see red "dots" along the top border of the Firefox window. If I move the window, they stop. For a while. Then they're back, blinking like lights on towers. 5-10 at a time. It's always along the window border(s).


Partial solution for me currently is to put the affected apps into fullscreen mode.

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