Prepare the display
Gently clean the screen with a suitable cloth, following the manufacturer’s cleaning instructions. Dust can resemble a dark pixel. Use normal viewing brightness and avoid reflections. Move the test browser window to the monitor you actually want to inspect.
Inspect multiple backgrounds
Open the Dead Pixel Test and enter fullscreen. Check white, black, red, green and blue in turn. Use the arrow keys or colour controls to advance. Look at the centre and all four edges; move the controls out of your line of inspection by changing where you look.
Distinguish points from larger marks
A fixed dark point on bright backgrounds suggests a dead pixel; a persistently coloured point may be a stuck subpixel. Broad patches, uneven brightness, image retention and dust are different problems. See dead versus stuck pixels before describing the defect.
Check the result again
Keep the same location in view while changing backgrounds. A mark that moves with a browser image is part of that image. Take a photograph of a visible hardware defect if you need evidence: a screenshot normally captures the rendered image, not a faulty physical pixel.
What to do next
Do not press, rub or heat a suspect pixel. Check your monitor’s return or support terms for that model. The test is an inspection tool, not a repair. For other display questions, use the Screen Resolution Checker or the Refresh Rate Test; neither certifies panel quality.