Why are there lines on my monitor?

Vertical or horizontal lines on a screen come from the panel, the cable or the graphics card. A full screen color test and two quick swaps tell you which.

By Hardware Detective editorial team · Last updated September 30, 2026 · How we test

Lines on a screen look alarming and the cause can be anywhere along the path from the graphics card to the panel. The good news is that a few quick checks narrow it down. Better still, several of the possible causes cost nothing to fix.

The question you’re answering is simple: is the line being drawn by the computer, added in the cable or built into the screen?

Step 1: look at the lines on solid color

Open the dead pixel test, go full screen and step through each color. Note what the lines do.

• Fixed in the same place on every color: usually the panel. A failed row or column connection shows as a line that stays put whatever is on screen.
• A thin line that is always the same color, often bright on black: a stuck row or column driver in the panel.
• A line that is always dark, most visible on white: a dead row or column in the panel.
• Lines that shimmer, crawl or flicker: more often a signal problem in the cable or the connection.
• Lines only on some colors or only in certain parts of an image: often the graphics card or its driver.

Write down which pattern you see. The next steps confirm it.

Step 2: take a screenshot

Take a screenshot while the lines are visible and open it on a different device such as a phone.

• Lines in the screenshot: the computer is drawing them. Update or reinstall the graphics driver. If that doesn’t help, the graphics card may be failing, which is more likely if games crash or show colored speckles too.
• Clean screenshot: the lines are added after the signal leaves the computer. The cable or the monitor is responsible.

Step 3: swap the cable and the port

This is the most common fix for lines that flicker or move.

1. Unplug the video cable at both ends and plug it back in firmly.
2. Try a different port on the graphics card and on the monitor.
3. Try a different cable. A damaged or low quality cable can carry enough signal for a picture but not a clean one, especially at high resolution or high refresh rate.

If lowering the refresh rate makes the lines disappear, the cable is struggling with the bandwidth. The 144Hz guide covers which cable types carry which refresh rates.

Step 4: try the monitor on a different computer

Connect the monitor to a laptop, a games console or another PC.

• Same lines on another source: the monitor is at fault. If it’s new, return it. If it’s under warranty, claim it.
• Lines disappear: the original computer or its graphics output is the problem.

For a laptop screen, connect the laptop to an external monitor or TV instead. Lines on the laptop screen but a clean external picture means the laptop’s panel or its internal display cable is at fault.

Laptops: the hinge test

Laptop screen lines often come from the thin cable that runs through the hinge to the display. It flexes every time you open the lid and eventually cracks.

Open the lid slowly from closed to fully open and watch the lines. If they appear, disappear or change at certain angles, the hinge cable is almost certainly the cause. It’s a cheaper repair than a new panel on most laptops.

Pressure and heat

Gently press on the bezel near where a line starts. If the line changes, a connection along the edge of the panel is loose. Don’t press hard on the screen itself.

Lines that only appear after the monitor has been on for a while or only when the room is warm, point to a connection that fails as it expands with heat. Both are hardware faults worth taking to a repair shop or the manufacturer rather than trying to fix at home.

What lines aren’t

• Single dots are dead or stuck pixels, not lines.
• A horizontal split that moves during games is screen tearing, a timing issue rather than a fault.
• Faint bands across a gradient are banding from limited color depth. They’re normal on many monitors and don’t appear on solid colors.

Before a warranty claim

Take a photo of the lines on the color that shows them most clearly with the whole screen in frame. Note whether they appeared suddenly or after a drop or a knock. Most warranties cover panel faults but not physical damage, so that detail matters. The warranty guide covers how to document screen defects.