How to verify a pixel flaw on a second video input

A dot or tiny mark on your monitor may look like a bad pixel, but a cable, video port, or source can create a similar-looking artifact. Checking a second input helps you find out whether the problem stays in the same spot on the screen.

Use the same color patterns on each input and change one part of the setup at a time. The Display Test can show full-screen colors that make pixel flaws easier to see.

Check the flaw on both inputs

1. Connect a video source to the monitor's first input and open the Display Test on that source. Show solid colors, including white, black, red, green, and blue. Look for the mark from a normal viewing distance, then move closer without pressing on the screen.
2. Note the mark's position relative to the monitor's edges. Record which colors make it visible and whether it looks dark, bright, or tinted. A quick photo can help you compare later, but do not rely on a photo alone because cameras can create their own artifacts.
3. Switch the monitor to its second input using the monitor's input control. Show the same test colors from a source connected to that input. If possible, keep the computer, test page, and settings the same. If you use a different device or cable, write that down because you are changing more than one part.
4. Compare the mark's physical location on the panel, not its position inside a window. Check the monitor's built-in menu too. If the mark stays in exactly the same place over the menu and on both inputs, that is strong evidence the flaw is in the display panel.
5. If the result is unclear, test one variable at a time. For example, use the same source and cable on the second port, then try a known-good cable, then another source. Avoid changing the resolution, cable, source, and input all at once.

If you only have one source, you can move its cable to the second monitor input if the connector fits. This checks the monitor's ports, but it does not compare two independent video sources. Some computers also need a separate adapter for different input types, which adds another possible cause.

What the result means

The mark stays at the same screen position on both inputs

A mark fixed to the same physical spot, especially one that remains visible over the monitor's own menu, is likely a panel pixel or subpixel flaw. A subpixel is one of the tiny red, green, or blue parts that combine to make a pixel. If only one color pattern reveals it, a single subpixel may be stuck or failing.

The mark appears on only one input

The monitor panel is less likely to be the cause. The issue may be specific to that input, its cable, an adapter, or the connected device. Test the same source and cable on the other port, then swap only the cable, then the source. This helps narrow down which part changes the result.

The mark shifts, flickers, or changes with the picture

A true pixel flaw stays in one physical location. A mark that moves with content, flickers, or appears only during motion is more likely a video signal or graphics artifact. Try another cable and source before arranging a panel repair.

The mark is visible only on one color

That can still be a pixel defect. A pixel that stays bright against a dark pattern may be stuck, while a pixel that stays dark on bright patterns may be dead. The color test makes the defect easier to describe, but it cannot identify the exact internal failure.

How to narrow down the cause

1. Check the monitor menu. Open the monitor's own settings menu while the mark is visible. If the mark remains in the same panel location over the menu, the computer is not drawing it as part of the video image.
2. Reseat the video cable. Turn off the monitor and source, unplug both ends of the cable, and reconnect them firmly. Avoid forcing a connector. Check for bent pins or a loose adapter.
3. Try a different port with the same setup. Keep the source and cable unchanged when switching inputs, if the connections allow it. If the flaw appears only on one port, use another port for now and check the monitor warranty or support options.
4. Try a known-good cable and source. Replace only one item at a time. If the defect disappears after changing the cable, the cable or adapter was likely involved. If it follows a source to another display, investigate that source or its graphics output.
5. Check the computer's display output. On Windows 11, open Settings › System › Display and confirm the correct display is selected. On macOS, open System Settings › Displays and check the connected display. These settings can help with a blank or distorted output, but changing resolution is unlikely to repair a single panel pixel.
6. Restart the source and monitor. Turn both off, disconnect power for about 30 seconds, reconnect them, and repeat the color check. This can clear a temporary signal problem, but it will not repair a physically damaged pixel.

When the panel is probably faulty

If the flaw stays in exactly the same physical spot across both inputs, multiple sources, and the monitor menu, treat it as a display-panel defect. Check the monitor's warranty terms before attempting any repair. Pixel policies differ, and some require a certain number or pattern of faulty pixels before replacement is offered. Do not press, rub, or tap the screen to try to fix it, since pressure can damage nearby pixels or the panel.

When a stuck-pixel pattern may help

If the spot is a colored pixel that remains bright rather than a dark pixel, you can try the Stuck Pixel Fixer after documenting the result. It flashes colors in an attempt to free a stuck pixel, but it cannot repair dead pixels or a faulty input port, and it may not work. Stop if the flashing is uncomfortable or unsafe for you. See when flashing pixel patterns may be unsafe before trying it.

A second-input check is most useful when you keep the test pattern and setup consistent, then change one connection at a time.