Lines on Screen: How to Find the Cause and Fix Them

What the lines tell you at a glance

Before testing, note exactly what you see. It narrows the search, although only the tests below give you a firm answer.

Vertical lines on a monitor and horizontal lines on a TV are both covered by the same method. Direction on its own does not tell you the cause.

How to find the cause: the four step diagnosis

Each check removes one part of the chain between the image and your eyes. Do them in order and stop when you have an answer.

Step 1: take a screenshot

A screenshot saves the image the computer or phone has drawn, before it travels down the cable and before the panel shows it. Take one (Win + Shift + S on Windows, Cmd + Shift + 3 on a Mac, the usual button combination on a phone) and open it on a different device.

• Lines are in the screenshot: the image itself is wrong. Look at software, the graphics driver or the GPU. Your screen is probably fine.
• Screenshot is clean: the image was right when it left the software, so the problem is later in the chain: the output, the cable, the port or the display. Go to step 2.

Step 2: check the screen's own picture

Most displays can draw something on their own, without any signal from a computer. If the lines cross that image too, the display is at fault.

• Monitors: open the monitor's on screen menu with its buttons. Many monitors also have a built in self test; Dell says that if a problem shows in its integrated self test, the monitor itself needs repair, and if not, the cause is outside it. Your model's manual has the steps.
• TVs: run the picture test in the TV's support menu (Samsung paths are below). Samsung says that if there are no lines in the picture test, the TV is working fine and you should look at the cable and the connected device.
• Laptops: Dell laptops have an LCD self test (hold D and press the power button). On any laptop, watch the maker's logo at startup and the BIOS or UEFI setup screen: these are drawn before Windows or its drivers load. Lines there point to hardware.
• Phones: watch the boot logo and the screen in safe mode.

Step 3: swap the cable and the port

For monitors and TVs, unplug both ends of the video cable and plug them back in firmly. Then try a different cable, and a different port on both the computer and the display. If the lines go away, you are done: replace the cable. Samsung TVs from 2022 onward also have an HDMI troubleshooting test in Self Diagnosis.

Step 4: use a second display

Connect the computer to another monitor or TV, or connect another device (a laptop, a console, a streaming stick) to the problem screen.

• Lines appear on both displays from the same computer: the computer's graphics (driver or GPU) is the cause.
• Lines stay on one screen whatever you connect: that screen is the cause.
• Laptop screen has lines, external monitor is clean: Dell notes this points to a hardware problem with the laptop's own screen (the panel or its display cable), not the graphics chip.

Check lines with solid color screens

Solid colors make lines much easier to see and describe, which helps both your diagnosis and any repair ticket.

1. Open the dead pixel test or the screen test and go full screen.
2. Step through white, black, red, green and blue. A line of a single color that is missing or always lit shows clearly on the opposite color: a stuck green line stands out on black and on red; a dead line stands out on white. Our plain white screen is quickest for dark lines.
3. Note whether the line is the same on every color. A line fixed in place across all colors and all content is typical of a panel fault. Lines that change pattern, shimmer or move between colors point back toward the signal.
4. With the dead pixel test, turn on Mark a pixel and click on the line. The position is listed in screen pixels, which is handy for a warranty claim or a repair shop.
5. Now drag a window across the line in normal use. If the line stays fixed on the glass while content moves, it belongs to the display path, not to the app.

How to fix lines on a monitor or PC

1. Reset the graphics driver. On Windows press Win + Ctrl + Shift + B. Microsoft lists this as a first step for display problems caused by the driver.
2. Roll back, update or reinstall the display driver. In Device Manager under Display adapters, Microsoft suggests rolling back if the problem started after an update, otherwise updating, or uninstalling and restarting so Windows reinstalls it. Get the latest driver from the maker of your graphics card or laptop.
3. Check the cable and ports as in step 3 above. Also try a lower resolution or refresh rate for a moment: if lines disappear at a lower rate, the cable or port may not handle the higher bandwidth. The refresh rate guide covers cables and ports.
4. Update the monitor firmware if the maker offers updates, and power cycle the monitor by unplugging it from the wall for a minute.
5. Run the monitor's self test. If lines show there, the monitor needs service.
6. If lines show in screenshots and on a second screen, the graphics card is the likely cause. Remove any overclock, check that the card is seated and its power cables are connected, and contact its maker if the lines persist with a clean driver.

How to fix lines on a laptop or Mac

• Dell: run the LCD self test by holding D and pressing the power button; release D when the screen flashes colors. Dell says lines during this test point to the LCD panel and suggests contacting support. If the test is clean, update the graphics driver and BIOS.
• Other Windows laptops: watch for lines on the startup logo and in the BIOS or UEFI setup screen. Lines there appear before Windows loads, so they are hardware. No lines there but lines in Windows points to the driver.
• Mac: connect an external display. If it is clean, the Mac's graphics are working and the built in screen or its cable is the problem. Run Apple Diagnostics (on Apple silicon, hold the power button until startup options appear, then press Cmd + D; on Intel, hold D at startup). Apple says to note the reference code for the service provider.
• Lines that change when you move the lid: tell the technician. A fault that reacts to movement points to a connection rather than to software.

How to fix horizontal or vertical lines on a TV

1. Run the picture test. On Samsung TVs from 2022 onward: All Settings, Support, Device Care, Self Diagnosis, Picture Test. On earlier Samsung models: Settings, Support, Self Diagnosis, Picture Test. Other brands have similar tests in their support or picture menus; check your manual.
2. No lines in the test? The panel is fine. Replace the HDMI cable of the device that shows lines. If lines remain, troubleshoot that device (cable box, console, streaming stick), as Samsung advises.
3. Update the TV software and power cycle it: Samsung suggests unplugging the TV for 60 seconds.
4. Lines in the picture test? The TV needs service. Samsung asks for the model code, software version and serial number when you book it.

Lines on a phone screen, including a green line

• Restart the phone and check whether the line survives.
• Take a screenshot. If the line is not in the screenshot, the phone's image is fine and the display is at fault.
• Try safe mode. On a Pixel, Google explains that if a problem goes away in safe mode, an app is likely the cause. Remove recent apps one at a time.
• Update the software.
• Still there? A line fixed in the same place, such as a single green, pink or white vertical line, is a display hardware fault. Contact the maker or an authorized repair shop and ask whether your model has any extended screen program; do not rely on a factory reset to fix a line that is not in screenshots.

Fixes that do not work

• Pixel fixer videos and flashing tools. These target single stuck pixels. A line is a whole row or column, or a signal fault, and flashing colors will not reconnect it. Our pixel fixer is only for stuck pixels.
• Pressing, tapping or heating the screen. Pushing on the panel or using a hair dryer can crack it or damage layers, turning a warranty repair into paid physical damage.
• Factory resets as a first step. If the line is not in screenshots, a reset cannot change it and only costs you time and data.
• Changing picture settings. Brightness, contrast or color settings can make a line less visible but do not remove it.

Warranty and repair

• Software, driver and cable causes cost little or nothing to fix.
• Lines in the self test, picture test, BIOS or boot logo mean the display needs service. On a new screen, contact the seller or maker straight away; lines are a clear fault, unlike a single pixel, which some policies tolerate.
• Physical damage (cracks, impact marks, pressure) is not covered by standard warranties such as Samsung's. Check whether you have accidental damage cover.
• Record the evidence: photos of the line on each solid color, the self test result, any reference code from diagnostics (Apple asks for it), and when it started.
• Repair or replace? Get a written quote before you approve a panel repair and compare it with the price of a new screen. Samsung itself notes that for a physically damaged TV, buying a new one may cost less than a repair.

How to prevent lines on screen

• Do not press on the panel, and carry laptops closed without anything between the keyboard and the screen.
• Avoid sharp bends in video cables and do not let them hang by the connector.
• Use cables rated for your resolution and refresh rate.
• Keep drivers and firmware updated, and install graphics drivers from the chip or laptop maker.
• Test a new screen on day one with the screen test so any fault is found inside the return window.