What causes lines on a laptop screen

A black line on a laptop screen often points to a damaged display panel, a loose internal cable or a graphics driver problem. A few quick tests will pinpoint the fault.

Restart the computer to check the startup screen

Hardware faults often show up as soon as the computer powers on, while software glitches tend to appear after the operating system loads the display drivers. You can use this timing to figure out where the problem lives.

Turn the computer all the way off. Press the power button and watch the display closely. The manufacturer logo will appear first against a dark background. Look for the black line on this initial startup screen.

If the line shows up right away, the physical screen, its internal cable or the graphics hardware is the likely cause. The operating system has not loaded yet, so a software update or display driver is a less likely cause.

If the startup screen is clear, the screen hardware may be fine. A line that appears only after the operating system loads points to a software issue such as a display driver problem. A driver fix is often quick, but not always.

Plug in an external monitor to isolate the hardware

Connecting a second screen tells you if the graphics card is sending out a clean image. You will need a standard HDMI or USB-C video cable. You also need a television or a desktop monitor.

Plug the cable into the side of the laptop and connect the other end to the external screen. Use the television remote or the monitor buttons to select the correct input channel. The computer may detect the new display automatically. Look at the external monitor to see if the black line appears there too.

Sometimes you have to press a button on the laptop keyboard to force the image to the second screen. Look for a function key with a picture of a monitor on it.

A clean external display usually means the graphics chip is working properly, so the problem is likely in the built-in screen or the ribbon cable connecting it to the motherboard.

If the black line shows up on both screens, the built-in panel is probably fine and the image is likely flawed before it reaches the screen. A driver problem is the first thing to rule out, though a graphics hardware failure is possible.

Booting into Safe Mode

You can double check a software fault by booting the computer into Safe Mode. This starts the machine with a basic display driver.

If the screen looks clear in Safe Mode, the regular display driver or other software is the likely cause. If the line remains in Safe Mode, a hardware problem is more likely.

Update or roll back the display driver

A faulty graphics driver can cause persistent lines across the desktop. Fixing this involves opening the device settings and telling the computer to refresh the software. You can do this without opening the laptop case or touching any internal wires.

On a Windows laptop, click the start menu and type Device Manager into the search bar. Open the app and look for the Display adapters category. Click the small arrow next to it to show your specific graphics card. Right-click the name of the graphics card and select Properties.

Click the Driver tab at the top of the new window to see your options. Click Update Driver and select the option to search automatically. The computer will look for a fresh version and install it. Restart the machine to see if the line disappears.

Sometimes a bad update is the cause of the problem. If updating does not work, go back to the same menu and click Roll Back Driver. This removes the current version and restores the previous software.

If the roll back option is grayed out, you can click Uninstall Device instead. Check the box to remove the driver software if it asks, then restart the computer. Windows often reinstalls a basic driver on its own after the restart. A bad driver can sometimes cause strange color tints, one reason a laptop screen looks yellow or blue at times.

Move the lid slowly to test the display cable

A thin ribbon cable routes video data from the motherboard to the screen. This delicate cable usually runs through the hinge mechanism. Opening and closing the lid flexes this wire bundle every single time. Years of daily use can pinch the internal wires or pull the connector slightly loose.

Turn the computer on and open the lid to a normal viewing angle. Pinch the top corner of the plastic frame and move the lid back and forth very slowly. Watch the black line on the display as the hinge moves.

A loose cable often reacts to the physical movement. The line might flicker, change colors or disappear entirely at certain angles. You might even see new horizontal lines flash across the display as the wires shift inside the hinge casing.

If the lines change when you move the lid, the screen panel is likely fine. The display cable may need to be reseated or replaced. That means opening the case, so ask a repair shop for a quote.

If the line stays perfectly still while you move the lid, the cable is less likely to be the cause and the display panel itself becomes the main suspect.

What vertical and horizontal lines usually point to

The shape and direction of the lines offer clues about which component is failing. Pay attention to how the marks look against a plain white background.

Solid black lines

A solid black line often points to damage inside the panel. The affected row or column may have stopped receiving power, and that kind of damage usually means a new screen. You might also notice a black spot on a laptop screen nearby. A dark spot can point to physical damage as well.

Colored vertical lines

Colored vertical lines can point to a fault inside the screen assembly or its connection, and they often mean the screen itself needs service. Avoid pressing on the screen or bezel to test it, since that can add damage.

Horizontal lines

Horizontal lines can point to a graphics, cable or panel fault, and a technician can narrow it down. The external monitor test above helps, because lines that also appear there suggest the graphics side. Impact damage can also leave bars across the screen.

Decide between repair and replacement

A display cable repair is often less costly than a new panel, but ask a repair shop for a quote on both. You have to weigh the price of the screen against the age of the machine.

Checking your coverage

Before you pay for a repair, check if the manufacturer will foot the bill.

• Find the serial number printed on the bottom casing.
• Type the serial number into the manufacturer support website.
• Check the active warranty status and expiration date.
• Review any extended protection plans tied to the machine.

Pricing the replacement parts

If the warranty has expired, look up the exact model number printed on the bottom of the computer. Search online for replacement screens to see what the bare part costs. Prices vary by model, so compare quotes before you decide.

Labor adds to the final bill if you hire a shop. A technician has to pry off the bezel and carefully route delicate cables. Paying for a new screen and the labor to install it can exceed the value of an older machine.

Replacing the laptop

If the computer is older, compare the repair quote with the cost of a replacement. A new machine usually comes with a fresh warranty and a new battery. You might want to choose a budget laptop instead of sinking cash into a failing device.

If you decide to keep using the old computer, you may be able to live with minor damage. A line from dead pixels often stays put, but lines caused by a failing cable or physical damage can change or get worse, so keep an eye on it.