Horizontal line on the screen

Hello Sinasi1,

It sounds like you are starting to see horizontal lines appear on the screen of your MacBook Pro.

You can try some isolation and troubleshooting steps. Here are some resources that can help:

• Restart your Mac: Log out, sleep, wake, restart, or shut down your Mac.

• Test in safe mode as it can help you determine whether issues you’re experiencing are caused by software that loads as your Mac starts up. How to use safe mode on your Mac
  • As it also " It also does a basic check of your startup disk, similar to using First Aid in Disk Utility. And it deletes some system caches, including font caches and the kernel cache, which are automatically created again as needed." if it doesn't happen when in safe mode, restart your Mac and test again.

• Create a test user to see if it is something only related to your user account: Set up users, guests, and groups on Mac https://support.apple.com/guide/mac-help/set-up-other-users-on-your-mac-mtusr001/11.0/mac/11.0

• Reset your SMC, How to reset the SMC of your Mac, to see if it could be related to power or other features.

• Take notice when you see this, if it's when your computer starts up, when using a particular program, performing a specific task, or if it's always there as it can help isolate why you are experiencing this.

Hope this information helps.

Have a good day.

If possible, use the right adapters to connect to an external display to see if the issue reproduces itself on an external display, and if it reproduces in mirrored mode or both modes.

This will help diagnose if the onboard graphics chip is having an issue, or if it is just an issue connections inside the computer.

Either way, if the issue is consistently there, that will help diagnose if a repair is warranted by an authorized service center or sending in to Apple.