Running OS X Yosemite on a mid 2012 13-inch MacBook Air, I've noticed that flashing bars will occasionally appear on the screen for no apparent reason. Sometimes these bars are solid colors (often green) or occasionally a sort of weird interlaced black and grey. These bars do not interfere with normal computer operation, and can often be cleared by forcing that portion of the display to refresh, such as by moving a window over it. However, rarely, these bars will cover the whole screen and refuse to disappear.

I am not aware of a way to reproduce this issue, and in all cases restarting the computer resolves the issue. It can appear on both the laptop's display and any connected external display.

I have confirmed this issue with another person who uses the same model of computer. Has anyone else seen this issue? Is there some way to prevent it from recurring?

2 Answers 2


I am experiencing the same issue. It seems to randomly happen unless the system is under load then it is more likely to occur.

I am more easily able to reproduce the issue by uploading large amount of content to the cloud such as a 5 gigabyte family movie, while watching a streaming video on the internet. The issue will usually occur within a few minutes. Remember to keep some of your desktop visible, about 3-4 inches on either side of the active window. When the issue occurs, any screen updates to the area where it occurs will clear it. The issue is also occasionally followed by a sudden system reset.

Most of the time refreshing the display where it occurs will make it disappear. You can not capture the anonymily with screen capture, you can try but it the capture image will show no display issues. I found shooting a video of the machine exhibiting the issue and then trying and succeeding to reproduce the issue in front of the a Genius at the Genius Bar got the quickest attention.

Typically the bars are on either side of the active window but they can show up somewhere in the middle of the active window. I took my MacBook Pro to Apple who at first couldn't find anything wrong in house, they sent it off to the shop and it was diagnosed with having a malfunctioning logic board which had also damaged the display. Both parts were replaced and I've had the system a few days and the issue has already started to re-occur. I am beginning to suspect it maybe a glitch in Yosemite when running on this model, that or a possible hardware issue made worse by using Yosemite.

The system passes the Apple Hardware Test (Short & Long) both before and after the logic board and display were replaced. I have also replaced the ram and the hard disk, and reinstalled Yosemite before I took it to the Genius Bar. Non of these helped to eliminate the issue.

My model is: http://www.everymac.com/systems/apple/macbook_pro/specs/macbook-pro-core-i5-2.5-13-mid-2012-unibody-usb3-specs.html

Use this link to determine your Mac's correct model number by serial number: http://www.everymac.com/ultimate-mac-lookup/

If you have experienced this issue please add a post in this area explaining what is happening, how if you can produce it, what you have done to try and remedy the issue, and have your efforts eliminated it.

  • I have this too. It happens on both my laptop screen and external display; usually it's a bar ~10px high, and can span anywhere from 1/4 to nearly the full length of the screen, with periodic breaks. Dragging the mouse through it does not affect it, but if I open the context menu or drag a window across it, the bars go away where I updated the screen. I have the exact same system you do, too.
    – Doktor J
    Commented Nov 6, 2015 at 23:21

Mid 2012 MacBook Air here. Seeing the same issue. There's a rectangular bar in the middle of the screen that is flickering. Last time it was red, but can be different colors. It's about 100 x 30 pixels or so.

As others have changed out all the hardware with no results I am guessing it's a software issue. Probably the graphics driver in Yosemite.

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