Horizontal or vertical lines on a computer monitor can be caused by anything from a loose cable to a failing display panel.
Before assuming the monitor is broken, it is worth checking the connection, graphics settings and another device.
The pattern and behavior of the lines can help identify the source.
01
Check the display cable
Start with the simplest possibility.
Disconnect and reconnect the HDMI, DisplayPort or USB-C cable at both ends.
Inspect the cable for visible damage.
If you have another compatible cable available, test it.
A poor connection can create flickering, artifacts or intermittent lines.
02
Try another port
If your computer or monitor has multiple display ports, switch to another one.
A damaged connector can cause signal problems even when the cable itself is fine.
Testing another port helps isolate the issue.
03
Restart the computer and monitor
Power down both devices completely.
Disconnect the monitor from power briefly, then reconnect everything and restart.
Temporary graphics or display-handshake issues can sometimes disappear after a full restart.
04
Test another device
Connect the monitor to another laptop, desktop or console.
If the lines remain visible, the monitor is more likely to be responsible.
If the problem disappears, investigate your original computer's GPU, drivers or output settings.
06
Update or reinstall graphics drivers
Graphics-driver problems can cause unusual artifacts.
If the lines appeared after a recent update, restarting or reinstalling the driver may help.
Avoid assuming the newest driver is always the cause, though. Hardware and cable problems are also common.
07
Can refresh rate cause lines?
An unsupported or unstable refresh-rate configuration can cause visual problems.
Set the monitor to a standard supported refresh rate and resolution.
If the problem disappears at a lower refresh rate, the cable, port or display may be struggling with the selected bandwidth.
08
Could the monitor panel be failing?
Yes.
Permanent vertical or horizontal lines can be caused by panel, internal ribbon-cable or electronics failures.
If the same line appears on every input and even over the monitor's own menu, hardware failure becomes more likely.
If replacement is necessary, see our monitor buying guides.
09
Practical checks before you continue
Start by noting whether the line appears before the operating system loads. A line visible in the monitor menu or on a no-signal screen points toward the display. If it appears only inside one application, capture a screenshot and open it on another device.
Power down before reseating cables, then test one known-good cable and another port that support the required resolution and refresh rate. Avoid changing several settings at once. Our monitor resolution explainer helps verify a supported signal.
Connect the monitor to another computer, or connect the computer to another display. This swap is the quickest way to separate a panel fault from a graphics or software problem. If motion trails rather than fixed lines are the issue, see our monitor ghosting guide.
Do not press, twist or strike the panel to remove a line. Physical damage and failed internal connections require professional repair or replacement. Compare warranty coverage before opening anything, and use our home-office monitor guide if replacement is the sensible outcome.
Lines that change when you move a laptop hinge may indicate the internal display cable rather than the graphics software. Do not repeatedly flex or press the panel. Back up important work and arrange service before an intermittent connection becomes a complete display failure.
If the problem follows the computer to another monitor, reinstalling the correct graphics driver or removing a recent faulty update may help. Use the computer maker or graphics manufacturer as the driver source, and avoid unverified driver-download sites.
Sources and further reading
We use primary and specialist sources to check the principles in this article. Product recommendations are researched separately.
