Start by testing the cable, port, and monitor menu before you assume the screen is dead. Vertical lines often come from a loose video cable, a bad HDMI or DisplayPort socket, a driver problem, or a failing LCD panel. Dell lists lines, distorted video, and flickering as common monitor symptoms that should be checked through cables, ports, settings, and diagnostics first [source: Dell].
TLDR: If your monitor shows vertical lines, first reseat the cable, try a different cable, and test another port or device. For example, if a laptop shows clean video on its built-in screen but lines on an external monitor, the fault is often the cable, adapter, port, or monitor rather than the graphics chip. A basic check can take under 10 minutes and may save you from replacing a $150 to $400 display for no reason. If the lines appear even inside the monitor’s own menu, the panel or internal board is likely at fault.
1. Check whether the lines come from the monitor or the computer
Press the monitor’s physical menu button. Open the on-screen display, also called the OSD. This is the menu built into the monitor itself.
If the vertical lines appear over the monitor menu, the issue is usually inside the monitor. That can mean a damaged LCD panel, a loose internal ribbon cable, or a bad control board. If the menu looks clean, the monitor may be fine, and the problem is more likely the cable, computer, adapter, driver, or graphics card.
This test is simple and very useful. It separates the monitor from the computer without installing anything. Honestly, it feels like this one check gets skipped too often, then people waste an hour reinstalling drivers that were never the problem.
2. Reseat the video cable at both ends
Turn off the computer and monitor. Unplug the video cable from the monitor and from the computer. Plug it back in firmly. Make sure it sits straight and fully inserted.
This applies to:
- HDMI
- DisplayPort
- USB C video
- DVI
- VGA, on older systems
Do not just wiggle the cable while everything is on. That can make a loose connection look better for a few seconds, then the lines return. Remove it, inspect it, and reconnect it properly.
Look for bent pins, crushed cable ends, cracked plastic, or a connector that feels loose. A damaged cable can create vertical lines, color bands, flashing, or random blackouts.
3. Try a different cable
A cable can fail even when it looks fine. This is common with cheap HDMI cables, old VGA cables, and USB C adapters that get moved every day.
Use a different cable that supports your monitor’s resolution and refresh rate. For example, a 4K 144 Hz monitor needs a cable and port that can handle that signal. If the cable cannot carry the data cleanly, the screen may show lines, flicker, or drop out.
If a new cable fixes the problem, stop there. Do not keep changing settings. Keep the fix simple.
4. Change the port
Move the cable to another port on the monitor. Then try another port on the computer. If your graphics card has three DisplayPort outputs, test each one.
If one port creates lines and another does not, you have found a strong clue. The bad port may be dirty, damaged, or failing. On desktop PCs, make sure the cable is plugged into the graphics card, not the motherboard video port, unless you are using integrated graphics.
For laptops, test another display output if possible. A USB C dock can also cause trouble. Remove the dock and connect the monitor directly to the laptop. Docks are convenient, but they add another failure point.
5. Test the monitor with another computer
Connect the monitor to a different laptop, desktop, game console, or media box. Use a known good cable.
Results matter here:
- Lines appear on every device: the monitor is probably faulty.
- Lines appear only on one computer: the computer, driver, GPU, or settings are likely involved.
- Lines appear only through one adapter: replace the adapter.
This is one of the cleanest tests you can run at home. It removes guesswork fast.
6. Restart and check BIOS or startup screens
Restart the computer. Watch the logo screen, BIOS screen, or recovery screen before Windows or macOS fully loads.
If the vertical lines appear before the operating system starts, the issue is probably hardware. That may be the monitor, cable, port, or graphics hardware. If the lines appear only after the desktop loads, the display driver or graphics settings may be causing it.
On Windows, you can enter BIOS or UEFI from startup or through recovery settings. Microsoft also recommends checking display drivers when dealing with screen flicker and related display issues [source: Microsoft].
7. Update or roll back the display driver
Driver problems can create strange lines, especially after a Windows update, GPU driver update, or new monitor installation.
On Windows:
- Right-click the Start button.
- Open Device Manager.
- Expand Display adapters.
- Right-click your graphics device.
- Choose Update driver.
If the problem started right after a driver update, choose Properties, open the Driver tab, and use Roll Back Driver if it is available.
It drives me crazy that some driver installers take several minutes, reboot the system, and still keep old settings that cause the same fault. If updating does not help, uninstall the driver cleanly and install the version from NVIDIA, AMD, Intel, or your computer maker.
8. Check resolution and refresh rate
Wrong display settings can create visual glitches. This is more common after connecting a new monitor, using a splitter, or switching from HDMI to DisplayPort.
On Windows, go to Settings > System > Display > Advanced display. Set the monitor to its native resolution. Then choose a supported refresh rate, such as 60 Hz, 120 Hz, or 144 Hz.
On macOS, open System Settings > Displays. Select the correct resolution and refresh rate. If you use scaling, test the default setting.
If the lines vanish at 60 Hz but return at 144 Hz, the cable, port, or monitor electronics may not be handling the higher signal cleanly.
9. Disable overclocking and custom display modes
Monitor overclocking can cause vertical lines. So can custom resolutions created in GPU control panels.
Disable any custom refresh rate. Restore factory display settings in NVIDIA Control Panel, AMD Software, Intel Graphics Command Center, or your monitor software. Then test again.
Also turn off features such as extreme overdrive, low latency modes, or unusual color formats if the lines started after changing monitor settings. Set color depth to a standard value, such as 8-bit, and test.
10. Inspect for physical damage
If the lines appeared after a drop, pressure mark, spill, or hit to the screen, suspect panel damage. LCD panels are fragile. Even light pressure can damage internal layers.
Signs of physical panel failure include:
- Vertical lines that stay in the same place.
- Colored bands that never move.
- Black blotches or ink-like marks.
- Cracks under the glass.
- Lines that appear even with no computer connected.
Panel damage is rarely worth repairing on budget monitors. On high-end displays, get a repair quote first. Compare it with the cost of a replacement.
11. Run the monitor’s built-in diagnostic test
Many Dell, HP, Lenovo, LG, and Samsung monitors include a built-in test pattern. It may show red, green, blue, white, and black screens. These patterns help reveal panel defects without using a computer.
Check your monitor manual for the exact button sequence. If vertical lines show during the built-in test, the monitor hardware is the likely cause.
When to replace the monitor
Replace or repair the monitor if vertical lines appear on the built-in menu, on multiple devices, with multiple cables, and during diagnostic screens. At that point, you have ruled out most external causes.
For a monitor under warranty, contact the manufacturer before opening the case. Opening it can void coverage. For an out-of-warranty display, repair makes sense only if it is a costly professional model. For many standard monitors, replacement is the safer choice.
Quick checklist
- Check the monitor menu. Lines on the menu usually mean monitor hardware trouble.
- Reseat the cable. Do both ends, not just one.
- Try another cable. Use one rated for your resolution and refresh rate.
- Switch ports. Test both monitor and computer ports.
- Use another device. This confirms whether the monitor follows the fault.
- Check BIOS or startup screens. Lines before the OS loads usually point to hardware.
- Update or roll back drivers. Do this if the issue appears only after login.
- Reset display settings. Use native resolution and a safe refresh rate.
The safest repair path is simple: test the easy external parts first, then move toward drivers, settings, and hardware failure. Vertical lines look serious, and sometimes they are. But a loose cable or bad adapter can look exactly like a dying screen, so rule that out before spending money.