What causes lines on your monitor

Lines on your monitor usually come from one of three sources: a loose or damaged cable connecting the monitor to your computer, interference from nearby electronics, or a failing display panel. The type of line — whether it's horizontal, vertical, flickering, or stationary — tells you which one is most likely the problem.

A loose video cable is the most common culprit. The cable that runs from your graphics card or motherboard to the monitor carries the video signal, and any break in that connection shows up as lines, static, or a completely blank screen. Even a partially loose connector can cause intermittent artifacts that come and go.

If the lines appear only when certain devices are nearby — a microwave, wireless router, phone charger, or USB hub — then electromagnetic interference is the cause. These devices emit radio signals that can disrupt the video signal traveling through your cable, especially if the cable is unshielded or routed too close to the source.

When lines persist even after you've checked cables and moved interference sources away, the monitor's internal display panel or electronics may be failing. This is less common in newer monitors but becomes more likely as a monitor ages.

Key Takeaways

  • Reseat your video cable at both the monitor and computer end before trying anything else — this fixes most line problems in minutes.
  • Move potential interference sources like wireless routers, phone chargers, and USB hubs at least two feet away from your monitor cable.
  • If lines appear only in certain programs or at certain resolutions, the issue is usually software-related rather than hardware damage.
  • Horizontal lines that flicker are typically cable or interference problems, while vertical lines that stay in one spot suggest a failing display panel.

How to fix a loose video cable

Start by powering off both your monitor and computer completely. Locate the cable running from the back of your monitor to your computer — this is usually a DisplayPort, HDMI, DVI, or VGA cable depending on your monitor's age and type.

At the monitor end, grip the connector firmly and twist it counterclockwise if it has a threaded collar (VGA and DVI cables), or straightforward pull it straight out if it's a push-fit connector (HDMI and DisplayPort). Wait five seconds, then reinsert it firmly until you hear or feel a click. If the connector has a threaded collar, twist it clockwise until snug — do not over-tighten.

Repeat the same process at the computer end. If your computer has multiple video ports, make sure the cable is plugged into the correct one. On most modern computers, the dedicated graphics card port is separate from the motherboard port, and using the wrong one can cause display problems.

Power both devices back on and check whether the lines are gone. If they persist, try a different video cable if you have one available — this tells you whether the cable itself is damaged rather than just loose.

Identifying and moving sources of interference

Electromagnetic interference typically shows up as horizontal lines that shimmer or flicker across the screen, often in a regular pattern. The lines may get worse or better depending on what devices nearby are actively running.

Common sources include wireless routers, microwave ovens, cordless phones, USB 3.0 hubs, phone chargers, and some LED lights. Move your monitor cable at least two feet away from any of these devices. If your desk layout makes this difficult, try routing the cable through a different path — keeping it away from power cords and wireless devices makes a real difference.

If you cannot move the interference source, you can buy a shielded video cable designed to block electromagnetic noise. Shielded cables cost slightly more but are worth it if you work in an environment with many wireless devices or near industrial equipment. Make sure the cable type matches your monitor's ports — a shielded HDMI cable will not help if your monitor uses DisplayPort.

Test the change by turning the suspected interference source on and off while watching your monitor. If the lines appear when the device turns on and disappear when it turns off, you have found the culprit.

When the problem is software, not hardware

Lines that appear only in specific programs, or only at certain screen resolutions, usually point to a software issue rather than a failing monitor. This is especially true if the lines disappear when you restart the program or change the resolution back to the default.

Update your graphics card driver first — this is the software that tells your computer how to communicate with the monitor. Visit the website of your graphics card manufacturer (NVIDIA, AMD, or Intel) and read the latest driver for your specific card model. Restart your computer after installing the update.

If lines appear only in one program, try running that program in a different resolution or in windowed mode instead of fullscreen. Some older games and applications do not handle modern monitor resolutions well and produce artifacts as a result. Lowering the resolution or switching to windowed mode often clears the problem when ready.

If the lines appear across your entire screen at startup but disappear after a few seconds, your monitor may need time to warm up. This is normal in older LCD and LED monitors and is not a sign of damage.

Testing whether your monitor panel is failing

If you have ruled out cable problems and interference, and the lines appear consistently regardless of what program you are running, the monitor's internal display panel may be deteriorating. This is more likely if your monitor is more than five years old.

Look at the pattern of the lines. Vertical lines that stay in exactly the same spot on the screen, or horizontal lines that appear in bands across the display, suggest a failing panel. Lines that move around, flicker, or change appearance when you move the cable suggest a connection problem instead.

You can also test by connecting the monitor to a different computer using a different cable. If the lines appear on the second computer too, the monitor itself is the problem. If the lines disappear, the issue was with your original computer or cable.

A failing display panel cannot be repaired — the monitor will need to be replaced. However, if your monitor is still under warranty (usually one to three years from purchase), contact the manufacturer about a replacement or repair.

Preventing lines and artifacts in the future

Keep your video cable away from power cords, wireless devices, and sources of heat. Route cables along the back or underside of your desk rather than across the top where they are exposed to interference.

Avoid bending or kinking the cable sharply, and do not let heavy objects rest on it. Even small cracks in the cable's insulation can let interference in or cause signal loss.

If you use a monitor arm or mount, find the cable with cable clips or sleeves so it does not move around or get pinched. Movement and pressure on the cable over time can damage the internal wires.

When buying a replacement monitor or cable, choose shielded cables if your workspace has multiple wireless devices or if you have experienced interference problems before. The small extra cost is worth avoiding the frustration of lines and artifacts.

Frequently Asked Questions

Can lines on my monitor damage my eyes?

No. Lines and artifacts on your screen are a display problem, not a health hazard. They may be annoying to look at, but they will not cause eye strain or damage beyond the normal strain of looking at a screen for long periods.

Why do lines appear only when I move my mouse?

This usually means your video cable is loose or damaged. The movement of your hand or arm near the cable can shift it slightly, interrupting the signal. Reseat the cable at both ends and the problem should stop.

Do I need to replace my monitor if it has lines?

Not necessarily. Most line problems come from loose cables or interference, which you can fix in minutes. Only if the lines persist after you have checked the cable, moved interference sources, and tested with a different computer should you consider the monitor itself faulty.

Will a different type of video cable fix the problem?

Sometimes. If your monitor has multiple port types (HDMI, DisplayPort, DVI), try a different cable type to see if one works better than the others. Newer cable types like DisplayPort are generally more resistant to interference than older types like VGA.

What if the lines only appear on one side of the screen?

Lines that appear only in one area of the screen often indicate a failing display panel, especially if they are vertical and stationary. However, they can also result from a partially loose cable or localized interference. Check the cable connection first, then test with a different computer before concluding the panel has failed.