What causes horizontal lines and what you can do about them

Horizontal lines on an LCD monitor usually come from one of three sources: a loose cable connection, interference from nearby electronics, or a failing internal component. The good news is that the first two are fixable in minutes. The third means the monitor itself is reaching the end of its life, and you will need to replace it.

Start by checking the cable connections — this solves the problem in most cases. If that does not work, move the monitor away from other devices or try a different power outlet. If lines persist after both steps, the monitor's internal circuitry is likely failing, and replacement is the most practical option.

Key Takeaways

  • Horizontal lines most often come from a loose video cable or power cable, which you can reseat in under a minute.
  • Electromagnetic interference from phones, routers, or other electronics can cause lines; moving the monitor or using a different outlet may stop them.
  • If lines remain after checking cables and moving the monitor, the display's internal components are probably failing and the monitor should be replaced.
  • Do not open the monitor yourself — capacitors inside can hold a charge even when unplugged and cause serious injury.

Reseat the video cable connection

The video cable carries the image signal from your computer to the monitor. If it is loose or partially disconnected, the signal breaks up and appears as horizontal lines, often flickering or changing position.

Turn off the monitor and your computer. Locate the cable at the back of the monitor — it will be a thick cable with a connector that has either 15 pins (VGA, older monitors), a flat rectangular shape (HDMI), or a small rectangular shape (DisplayPort or USB-C). Grasp the connector firmly and pull it straight out. Wait five seconds, then push it back in until you hear or feel a click. If the connector has small screws on either side, tighten them by hand.

Turn the monitor and computer back on. If the lines are gone, the problem was the loose connection. If lines remain, move to the next step.

Check the power cable and try a different outlet

A loose power connection can also cause display problems. At the back of the monitor, locate the thick black power cable. Unplug it from the monitor, wait ten seconds, then plug it back in firmly until it seats completely.

Next, unplug the monitor's power cable from the wall outlet and plug it into a different outlet in the same room — ideally one that is not shared with other high-power devices like a microwave, space heater, or printer. Electromagnetic interference from these devices can travel through shared power lines and disrupt the monitor's display. If the lines disappear after switching outlets, you have found the source. Use the new outlet going forward, or plug the monitor into a surge protector on a dedicated circuit if one is available.

Move the monitor away from other electronics

Wireless devices and electronics that use radio frequencies can interfere with monitor signals even without sharing a power outlet. Cordless phones, cell phones, routers, and microwave ovens are common culprits.

If your monitor sits close to a router, phone charger, or other wireless device, move it at least two feet away. If that is not practical, move the interfering device instead. Turn off any nearby wireless devices temporarily to see if the lines stop. If they do, you have identified the source. You can then decide whether to keep the devices separated or accept the minor interference.

Test with a different video cable

If you have access to another video cable of the same type (HDMI, DisplayPort, or VGA), borrow it and connect it to your monitor. This rules out a cable that is damaged internally but appears fine on the outside. Damaged cables can cause intermittent signal loss that shows up as lines or color problems.

If the borrowed cable eliminates the lines, your original cable is faulty and should be replaced. HDMI and DisplayPort cables are inexpensive — usually between five and fifteen dollars for a quality cable. VGA cables are similarly priced. If you do not have access to a spare cable, skip this step and move forward.

When the monitor itself is failing

If horizontal lines persist after reseating cables, trying a different outlet, and moving the monitor away from interference, the monitor's internal components are likely failing. LCD monitors contain circuits that process the video signal and control the backlight. When these components age or fail, they produce visual artifacts like lines, discoloration, or flickering that cannot be fixed by the user.

At this point, repair is usually not worth the cost. Monitor repairs often run fifty to one hundred dollars in labor alone, and a new monitor of similar quality costs between one hundred and three hundred dollars depending on size and features. Most people find replacement more practical than repair.

Do not attempt to open the monitor yourself. Even when unplugged, capacitors inside the monitor can hold an electrical charge strong enough to cause serious injury or death. If you want a professional diagnosis before replacing the monitor, take it to a local electronics repair shop — they can open it safely and tell you whether repair is possible.

Frequently Asked Questions

Can I fix horizontal lines by adjusting monitor settings?

No. Horizontal lines are a hardware problem — either a connection issue or a failing component. Monitor settings like brightness, contrast, and refresh rate do not cause or fix them. If adjusting settings seems to change the lines, you are probably just noticing them more or less, not actually fixing them.

Do horizontal lines mean my monitor will stop working soon?

Not necessarily. If the lines came from a loose cable, fixing the connection means the monitor will work normally for years. If the lines are from interference, moving the monitor solves it permanently. If the lines come from a failing internal component, the monitor may continue working for months or years, but the problem will likely get worse over time.

Will a different video cable type fix the problem?

Switching from VGA to HDMI or DisplayPort will not fix lines caused by a loose connection or interference. However, if your monitor supports multiple cable types and one port is damaged, using a different port with the correct cable type may work. Check your monitor's manual to see which ports are available.

What if the lines only appear when I first turn on the monitor?

Lines that disappear after the monitor warms up for a minute or two usually indicate a failing capacitor or power supply component. This is a sign the monitor is aging. The problem will likely return more often and last longer as the component continues to degrade. Plan to replace the monitor within the next year.

Can I use my monitor with lines while I save up for a new one?

Yes, as long as the lines do not make your screen unreadable. If you use the monitor for detailed work like photo editing or design, lines may cause eye strain or make it hard to see colors accurately. For general web browsing or document work, minor lines are usually tolerable. If the lines get worse or spread, stop using the monitor to avoid potential electrical failure.