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How the Test Works

A pixel test isolates a single defect by stripping every distraction from the screen except one flat color at a time. Every pixel on an LCD or OLED panel is actually three sub-pixels — red, green and blue — sitting side by side, and a fault can hide behind normal content but announce itself instantly against a pure color field. That is why this tool cycles through solid red, green, blue, white, black and gray screens in sequence instead of showing one static pattern: a defect invisible on white can glow clearly on black, and one invisible on black can show up only against a saturated color.

There are two distinct failure types, and telling them apart changes what you can do about them. A dead pixel receives no electrical signal at all, so it stays black no matter which color fills the screen — the sub-pixel equivalent of a burnt-out bulb, and almost always permanent. A stuck pixel is different: it is receiving power, but its sub-pixel transistor is locked in one state, so it shows a single fixed color (commonly red, green or blue) on every background where it should be dark or a different shade. Stuck pixels sometimes recover on their own or respond to gentle stimulation; dead ones do not, since the problem is a broken connection rather than a frozen switch.

Run the sequence at normal working brightness, not maximum, and sit at a comfortable viewing distance — too close and even a flawless panel's sub-pixel grid can look irregular. Scan systematically: corners and edges first, since manufacturing defects cluster near panel borders, then sweep the rest of the surface in a grid pattern. Clean the screen with a microfiber cloth before starting; a single speck of dust or a faint fingerprint smudge looks exactly like a dead pixel from normal viewing distance, and it is the single most common false alarm people report.

What You Should Know

• Dead pixels are rarely fixable — the sub-pixel transistor has failed outright, so no software trick or physical technique restores power to it.
• Stuck pixels sometimes respond to treatment — cycling colors rapidly over the exact spot for several minutes, or, at your own risk, applying very light pressure with a soft cloth on an LCD panel while it is off, occasionally frees the transistor.
• Manufacturers publish pixel-defect policies, often based on the ISO 9241-307 classification, stating how many dead, stuck or always-bright sub-pixels are acceptable before a display qualifies for replacement — count precisely before contacting support.
• Test new displays immediately — return and warranty windows are short, and a defect documented on day one is easy to claim; one found weeks later invites disputes over when it appeared.
• OLED panels can show a related but different issue — slight sub-pixel non-uniformity or color shift at low brightness — which is not the same defect as a dead or stuck pixel and usually falls under separate policy terms.