MAPIWhy Are There Horizontal or Vertical Lines on My Monitor?
Lines on a monitor are persistent or intermittent bands, columns, or streaks that run across part or all of the displayed image.
Disconnect the normal video signal and run the monitor's built-in diagnostic if available. Dell specifically recommends this test for horizontal or vertical lines because it separates panel problems from the PC, graphics card, cable, and settings.
Key takeaways
- Lines that appear during the monitor's built-in diagnostic point more strongly to monitor hardware.
- Lines that disappear in self-test but return with the computer point to the signal path, graphics output, driver, or settings.
- A cable or port change is a low-risk way to isolate connection problems.
- Recent driver or refresh-setting changes can create display artifacts without physical panel failure.
What it actually means
Horizontal or vertical display lines are image artifacts that remain visible over normal content. They can originate in the monitor panel or electronics, or they can be introduced before the signal reaches the monitor.
The main explanation
Dell specifically lists horizontal and vertical lines as a condition for running built-in monitor diagnostics. If the abnormality is present in the diagnostic, the monitor is likely responsible. If the diagnostic is clean, the computer side becomes more likely: cable, graphics port, driver, refresh rate, or GPU. This isolation prevents unnecessary monitor replacement when the root cause is upstream.
Main causes and reasons
1. The video cable or connector is unstable
A damaged, loose, or marginal cable can corrupt the video signal and create visible line artifacts.
How to recognize it
- Lines change when the cable is moved
- Another cable removes the lines
- Built-in monitor diagnostics are clean
Why it matters: This is one of the easiest external causes to test.
2. The graphics driver or GPU output is producing artifacts
Driver problems or graphics hardware instability can introduce lines into the rendered image.
How to recognize it
- The lines appear in screenshots or on another monitor
- The issue began after a graphics change
- Updating or rolling back the driver changes the symptom
Why it matters: If multiple monitors show the same artifact from one computer, the PC side becomes more likely.
3. Refresh or display settings are unstable
Unsupported timing or refresh configurations can create visible artifacts on some setups.
How to recognize it
- Lines appear only at one refresh rate
- The recommended mode is stable
- Changing resolution or refresh alters the pattern
Why it matters: Returning to supported defaults is a useful test before hardware replacement.
4. The monitor panel or internal electronics are failing
Panel rows, columns, or driving electronics can create persistent straight lines.
How to recognize it
- The lines appear in the monitor self-test
- The same line stays in exactly the same position
- The artifact appears with multiple computers and cables
Why it matters: Lines in built-in diagnostics strongly support an internal monitor problem.
How to identify your situation
The monitor hardware is the leading cause.
Next: Use the manufacturer repair or warranty path.
The computer, cable, port, driver, or settings are more likely.
Next: Test a known-good cable and another video output, then review the graphics driver.
The GPU or computer-side signal path is more likely.
Next: Troubleshoot the graphics hardware and driver.
The previous timing or mode was unstable.
Next: Use a supported refresh rate and confirm cable capability.
What you can do
- Reconnect both ends of the video cable securely.
- Test a known-good HDMI or DisplayPort cable.
- Try another graphics output and another monitor input.
- Return resolution and refresh rate to supported recommended values.
- Update or roll back the graphics driver if the timing matches a driver change.
- Run the monitor's built-in diagnostic.
Common misconceptions
A cable, graphics output, driver, or unstable mode can also create lines.
A built-in diagnostic can show whether the monitor is actually responsible.
No signal means the monitor is not receiving usable video; lines mean an image is being displayed but contains artifacts.
When it may be a bigger problem
Seek manufacturer support if lines appear during built-in diagnostics or persist with multiple computers and known-good cables. If the monitor is physically cracked, struck, or liquid-damaged, use appropriate repair guidance rather than software troubleshooting.
Frequently asked questions
Can a bad HDMI cable cause vertical lines?
Yes. A damaged or marginal cable can create signal artifacts, so swapping in a known-good cable is a useful test.
Do vertical lines mean my monitor is broken?
Not always. If the lines also appear in the monitor's built-in diagnostic, hardware failure becomes much more likely.
Can a graphics driver cause horizontal lines?
Yes. Driver or GPU output problems can create display artifacts.
Should I test the monitor on another computer?
Yes. If the same lines appear with another computer and cable, the monitor itself becomes the stronger suspect.
Sources
- Fix Dell Monitor Display Issues — Dell SupportOfficial
- How to Run a Diagnostic Test on a Dell Monitor — Dell SupportOfficial
Written by Mapiance Editorial Team
The Mapiance Editorial Team researches, writes, reviews, and maintains practical guides and explainers for MAPIANCE.
Reviewed by Mapiance Editorial Team
Published Sep 5, 2026 · Updated Sep 30, 2026 · Verified Sep 3, 2026