Lines on an iPhone screen may appear for no obvious reason. Sometimes, they are a sign of a serious issue, such as a hardware or software fault, but they may also be due to a buggy app or glitch on the iPhone. If you can't work out why the screen shows lines and can't identify a rogue app, restart, reset or restore the iPhone.
Assess the Problem
Before troubleshooting, try to work out why the screen has lines and when it shows them.
Think about whether changes to the iPhone may have triggered the problem. For example, if lines first appeared after you dropped the handset or exposed it to water, they may be a sign of damage. If you dropped the iPhone, troubleshooting fixes may not solve the problem; if the handset is wet, dry the iPhone before you try to fix the screen to avoid more serious damage. If the screen has recently been replaced, it may not be connected correctly and you may need to have it fixed.
Use different apps to see if the lines appear on all of them. If they do, move on to troubleshooting; if the lines only appear when you use a specific app, delete and reinstall it.
Tap and hold the app on the Home screen until it starts to shake. Select the X that appears on the corner of the app to delete it.
Select Delete on the confirmation message and press the Home button to return to the regular Home screen.
Open the App Store, search for the app and select the Cloud Download button to reinstall the app. If the app still has screen lines, contact its developer for support.
Restart or Reset the iPhone
Sometimes, an iPhone gets a glitch that makes it stop working correctly. You may not be able to identify the problem but may be able to clear it by restarting or resetting the iPhone. Begin troubleshooting with a restart and use a reset if that doesn't work.
Perform a Restart
Press and hold the Sleep/Wake button. On an iPhone 6, this is on the side of the handset; on an iPhone 5, it's at the top. Hold down the button until the Slide to Power Off slider appears. Swipe the slider and wait for the iPhone to shut down. Press the Sleep/Wake button to restart.
Perform a Reset
Hold down the Sleep/Wake and Home buttons together. When the Apple logo appears, let go of the buttons. The iPhone shuts down, resets and restarts.
Restore the iPhone
If you still see lines on the screen after a restart and reset, try restoring the iPhone. This process wipes data and takes the iPhone back to factory settings. You can then restore most current settings using a backup or set up the iPhone as if it is new.
Connect the iPhone to the computer and open iTunes. Select the iPhone's icon and open Summary in the Settings area.
Go to the iPhone area and select Restore iPhone. You'll see a prompt to back up the iPhone. If you want to restore your key settings when you set up the iPhone after a restore, create the backup.
Select Restore and wait for iTunes to restore the iPhone. Do not disconnect the iPhone during the process. When the restore is done, follow the prompts to set up the iPhone as new or from the backup.