What causes horizontal lines on a monitor?

Horizontal lines point to the row-control circuitry rather than the column circuitry — specifically the gate driver, which sequentially activates each horizontal row of pixels during every refresh cycle. A failing gate driver, a damaged ribbon cable feeding it, a loose or damaged video cable, or physical pressure/impact damage to the panel can each fracture that row signal and freeze one row of pixels in place, showing up as a horizontal line.

How do I know if a horizontal line is physical damage or a fixable problem?

Gently press the bezel near where the line appears (with the monitor off first, then on) — if the line shifts, flickers, or changes with light pressure, it's very likely physical panel damage, which is not repairable at the consumer level. If pressing the bezel does nothing and the line is also visible in the monitor's own OSD menu or the PC's BIOS boot screen, the fault is internal but not damage-related — most often the gate driver or T-con board. If the line disappears in the OSD/BIOS screens entirely, the cause is upstream: the cable, GPU, or a driver setting.

Why do gate driver failures sometimes cause more than one line?

Gate drivers operate in a chained, 'bucket brigade' pattern — each gate driver chip controls a block of rows and passes timing data down to the next chip. If one chip fails, every row it controls and every chip after it in the chain can misfire, which is why a single gate-driver fault sometimes shows up as several horizontal lines or bands rather than just one.

Can a cable cause horizontal lines on a monitor?

Yes. A loose, damaged, or poorly seated HDMI, DisplayPort, or USB-C cable can drop individual signal lines within the connection, and depending on how the panel's timing controller interprets the dropped data, that can show up as a horizontal line as easily as a vertical one. Reseating the cable, removing any dock or adapter, and testing with a single known-good cable rules this out in under a minute.

Do horizontal lines mean the monitor needs to be replaced?

Not automatically. If the line disappears after reseating the cable, switching ports, or updating the GPU driver, the panel is fine. But if the bezel-pressure test confirms physical damage, or the line persists in the monitor's own OSD menu and BIOS boot screen with no external cause, the row electrodes or gate driver are compromised — and monitor panels are not economical to repair at the component level, so replacement is the practical fix.

Horizontal Lines on Your Monitor? How to Fix Them (2026)

Quick Answer: Horizontal lines on a monitor are usually one of four things, in order of how often each shows up: a loose or damaged video cable, a failing gate driver (the chip that activates each horizontal row of pixels in sequence), physical pressure or impact damage to the panel, or — less commonly — a GPU driver issue. A 10-second bezel-pressure test and the OSD-menu/BIOS-screen check used for vertical lines both apply here too, and together they tell you in under a minute whether you’re looking at a free cable fix or a panel that needs replacing.

Horizontal and vertical lines look similar but point at different internal circuitry. A vertical line usually traces back to the T-con board’s column drivers; a horizontal line traces back to the gate driver — the row-side circuitry that switches on one horizontal line of pixels at a time during every refresh. That distinction matters because gate drivers fail in a distinctive chained pattern that column drivers don’t, and horizontal lines are also the more common signature of physical panel damage.

Horizontal-line causes and fixes, ranked by likelihood

Cause	How to tell	Fix
Loose or damaged cable	Line flickers or shifts when the cable is touched or moved	Reseat both ends, remove docks/adapters, test with one known-good cable
Failing gate driver	Line(s) visible in the monitor's own OSD menu and BIOS boot screen; sometimes multiple lines/bands	Replace the monitor — gate driver sits on the T-con board, not economical to repair
Physical pressure or impact damage	Line shifts or appears when gently pressing the bezel near the line	Not repairable — the panel's row electrodes are physically fractured
Outdated or corrupted GPU driver	Started after a driver update; intermittent or app-specific	Clean-reinstall the latest driver from NVIDIA/AMD/Intel
Wrong or unstable input port	Line disappears on a different port (HDMI vs. DisplayPort)	Switch input port and cable type, retest

Two quick tests before you touch a cable

The bezel-pressure test. Gently press the monitor’s bezel near where the horizontal line appears — first with the display off, then on. If the line visibly shifts, flickers, or briefly changes under that light pressure, that’s a strong signal of physical damage to the panel itself: an impact, pressure point, or liquid ingress can fracture the horizontal row-electrode traces that gate drivers rely on. Lines caused by physical damage don’t move when you change resolution or input source, and they’re often accompanied by a faint dead zone or discoloration right at the line.

The OSD-menu / BIOS-screen test. Open the monitor’s own on-screen display menu, or restart the PC and watch the BIOS/UEFI boot screen. Neither receives a signal from Windows, the GPU, or any app — both are generated entirely inside the monitor. If the horizontal line shows up there too (and the bezel-pressure test came back clean), the fault is an internal gate-driver issue rather than damage. If the OSD and BIOS screens look completely clean, the cause is upstream — cable, GPU, or a driver/refresh setting — and it’s fixable for free.

ASUS ProArt PA278QV — Best Replacement If It's the Panel

Best if the pressure or OSD test confirms hardware · 27" QHD IPS · factory-calibrated · about $230

Factory color-calibrated at the panel level, so a fresh unit isn't inheriting whatever gate-driver drift or row-electrode fault the old one developed.
ASUS backs its ProArt line with a standard multi-year warranty covering panel and internal component defects — the exact fault category a gate-driver or physical-damage line falls into.
The right pick once the bezel-pressure test and the cable/driver checks below have ruled out everything fixable for free.

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If both tests come back clean

Reseat the cable at both ends. Unplug and firmly replug the video cable at the monitor and the GPU, removing any USB-C dock, KVM switch, or adapter from the path while testing.
Test with a single known-good cable. Swap in a different HDMI, DisplayPort, or USB-C cable outright rather than just reseating the existing one — a damaged cable can look fine externally.
Switch input ports and cable types. If the line disappears on HDMI but appears on DisplayPort (or vice versa), the fault is isolated to that specific port or cable rather than the monitor.
Clean-reinstall the GPU driver. Use the manufacturer’s official uninstall-and-reinstall tool rather than updating over the existing driver.
Lower the refresh rate one step. A cable or port running near the edge of its bandwidth can drop bits during a redraw, which occasionally shows up as a horizontal line rather than a clean signal loss.

Horizontal lines by the numbers

Chained failures. Gate drivers operate in a “bucket brigade” pattern — each chip controls a block of rows and passes timing data to the next chip below it — which is why a single gate-driver fault can cascade into several horizontal lines or bands instead of just one, unlike most single-column vertical line faults.
Pressure-test in seconds. A line that visibly shifts under gentle bezel pressure is one of the fastest, free diagnostic signals for physical panel damage — no software or cables required to check it.

The bottom line

Run the bezel-pressure test first — it takes seconds and immediately flags physical panel damage, which isn’t repairable. If that comes back clean, check the OSD menu and BIOS boot screen next; a line that shows up there too points to the gate driver, and a factory-calibrated replacement like the ASUS ProArt PA278QV is more practical than a component-level repair. If both tests come back clean, work through the cable, port, driver, and refresh-rate checks above — most horizontal-line cases resolve there for free. Seeing a different pattern instead? Our monitor vertical lines guide covers the column-driver side of the same problem, our monitor flickering guide covers strobing and brightness-linked issues, our monitor ghosting guide covers trailing and motion-blur issues instead of line artifacts, and our monitor artifacts guide covers blocky or shifting corruption that isn’t confined to a fixed line.