Why Are There Horizontal Lines on Mac Screen – How to Fix

Do you have lines across your Mac’s screen? That might be due to several reasons like a damaged screen, overheating, screen burn-in, or some internal damage to the wiring connecting to the screen. This can also be due to issues like outdated drivers, software, or power management issues. This article details the various reasons for this issue and how to deal with them.

You can fix the Horizontal Lines on Mac Screen through multiple methods. The first thing you can do is simply restart your Mac and then check if the lines are gone. Another method you can try is closing all the applications that might be causing the overheating issue, such as Chrome tabs and others. Ultimately, you can reset the SMC by following certain steps.

A screen burn-in is uncommon but not unheard of these days. It was more prevalent during the earlier years when images would be permanently burnt into the screen if a static image was displayed on the screen for an extended period of time.

However, that is unlikely to be the issue, as that does not happen with modern-day LCD screens. The T-CON board issue can be another cause which is a design flaw that we’ll talk about later. 

Why Are There Horizontal Lines on Mac Screen and How To Fix

The lines on your Mac’s screen might be due to some complex hardware issue or software problem that can be fixed easily. So, it would be a good idea to check out some solutions before going to an Apple service center. Here are some possible methods that you can try out. 

1. Restart your Mac

If you see horizontal or vertical lines for the first time, you should try restarting your Mac first to see if it fixes the problem.

Why Are There Horizontal Lines on Mac Screen
Horizontal Lines on Mac Screen

A restart fixes a lot of commonly faced problems on the Mac. 

2. Overheating issue

If your Mac is getting warmer than usual, try lowering its temperature and letting it cool down before checking to see if it fixes the problem. 

3. Utilize maintenance scripts

Your Mac periodically cleans temporary log files and other non-essential items. However, sometimes they might not run as frequently as they should. You can try running them manually to see if it removes the lines on your screen.

Various third-party applications can be used to do this, like CleanMyMac X, which has an option to run maintenance scans on your system. 

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4. Check the connection

If you use a Mac with an external display, you can check to see if the physical connection between the CPU and the display is connected correctly. Loose connections can also lead to lines appearing on your screen. 

5. Use an alternate display

If you use a Mac with an external monitor, you can try using a different monitor to see if there’s an issue with your current monitor. Try switching between other HDMI ports, as some ports might be damaged, leading to this issue.

After switching out to another screen, if the system boots up without any lines on the screen, it is most likely a physical issue with your primary display. 

6. Reset the SMC

The Systems Management Controller, aka SMC, is responsible for managing the power supplied to your system during boot-up. So, if the lines on your screen are due to some sort of power management issue, then this should be able to fix it.

If you have a Mac running on Apple’s silicon chip like the M1, M1 Max, or the M2, you can easily reset the SMC by restarting the system when it is plugged in. However, resetting the SMC is a bit different if you have a Mac with an Intel chip.

Macs running on an Intel chip without the T2 security chip can reset their SMCs by shutting down the Mac, holding the Shift-Control-Option keys and the power button for ten seconds, and releasing them. 

If you use a Mac with a T2 security chip, then follow the steps given below to reset the SMC:

  • Shut down your Mac 
  • Hold down the Control button on the left side of the keyboard, Options button on the left side, and the Shift key on the right side. When you hold all three of these buttons together, your Mac may turn on.
Why Are There Horizontal Lines on Mac Screen
  • Hold the buttons for seven seconds and press the power button. 
  • Hold all four buttons for another seven seconds, then let them go. 
  • Wait a couple of seconds, and then restart your Mac. 

If you use Mac with an external display with the T2 chip, then use the following steps to reset the SMC.

  • Shut down your Mac and disconnect the power. 
  • Wait for fifteen seconds and then reconnect the power cable. 
  • Wait for five seconds more, and then turn your system back on. 

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How to Fix the T-CON board Display Issue?

The solutions mentioned above should be tried at least once before going to the Apple service center. However, another issue has plagued a couple of MacBook models: the T-CON board display issue. 

If you notice greyish horizontal lines coming from the bottom of your screen and appearing abruptly if the Mac is used for too long, then it might be due to the T-CON board issue. This is due to a design flaw.

However, that has not been acknowledged by Apple yet. This issue is more prevalent in the 13-inch non-touch bar Macs from 2016 and 2017, as these models have a single fan leading to insufficient heat management. Moreover, dust-build, faulty heat sinks, and poor air circulation can cause this problem. 

However, to resolve this issue, you must have your entire screen replaced, which can be pretty heavy on the wallet. The T-CON board is directly connected to the display assembly, and the board alone cannot be returned. If your device is still within the warranty period, you can ask for a free replacement by walking into any Apple-authorized service center. 

If you want to prevent this issue, ensure you keep your Mac clean and cool. Ensure that your Mac has clean vents, properly working fans, and good thermal paste to manage the thermal conductivity properly. Do not use the laptop on a pillow or soft surface like the bed as that might block the air vent causing the system to heat up. 


Here is all you need to know on everything you can try to fix the issue of Horizontal lines on Mac Screen. There could be multiple reasons for this, but the methods mentioned above will help you resolve it within no time. If at all nothing works, you can always take your system to the service center, and they might help you better.

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