The lines could be black, white, green, pink, or any other color. So you could very well get white stripes on your phone screen, black lines, or a combination of colors.

If so, the lines are caused by physical strain on the screen. You can try disassembling the screen to remove some stress, though this will void your warranty. For general instructions, see Resources.

"Persistent horizontal lines appear on the screen [of a 24-inch iMac], which significantly hampers the usability and visual appeal of the device," wrote user latVm on Apple's discussion forum.

99% of the time, vertical lines on screen are due to hardware defect so there’s no amount of software tweak that you can do to fix this on your end. Post Tags: # Samsung Galaxy S9.

I noticed that when the phone wakes up, horizontal lines flash on the screen. It does that randomly, not every time the phone wakes up. Sometimes it's just 1 line, sometimes it's multiple.