White Dead Pixel Test
A white dead pixel test fills your screen with pure white (#FFFFFF) to reveal dead pixels — pixels whose transistor has permanently failed, leaving them always dark regardless of what the screen is displaying. Against a pure white background, dead pixels are maximally visible: the contrast between a black dead pixel and the surrounding white is 100%, making single-pixel defects detectable at normal viewing distance. This makes the white test the primary diagnostic for dead pixel warranty claims. The ISO 13406-2 Class II standard — which most consumer monitors are certified under — allows up to 2 Type 2 defects (permanently dark pixels) per million pixels. A 1920×1080 display has approximately 2.07 million pixels, permitting up to 4 dead pixels under Class II tolerance. In practice, most premium monitor brands (Dell, LG, ASUS ROG, Samsung) now offer 'pixel perfect' or zero-dead-pixel warranty policies on their higher-tier displays, meaning a single visible dead pixel qualifies for replacement. White is also the diagnostic color for the dirty screen effect (DSE): grey smudges, vertical bands, or cloudy patches visible on flat white or light-grey backgrounds but nearly invisible on varied content like photos and video. DSE is most common on VA panels and large IPS displays, and most disruptive during word processing, spreadsheet work, or document editing on white backgrounds. Unlike the black dead pixel test — which requires a dim room to spot backlight bleed and IPS glow — the white test works accurately in normal ambient lighting. Run it at your regular viewing distance and scan systematically from corner to corner. Any black dot, color fringe, or dark smudge on the white screen is a genuine display defect worth documenting before a warranty claim.
Ready to scan your monitor
The test displays 6 solid colours in full-screen — Black, White, Red, Green, Blue, and Gray. Scan the entire screen for any pixel that doesn't match.
Click or → next colour · ← previous · Esc exit
What Do Dark Spots on a White Screen Indicate?
| Defect Count | Rating |
|---|---|
| 0 defects | Perfect |
| 1 dead pixel | Acceptable |
| 2–5 defects | Borderline |
| 6–10 defects | Degraded |
| 11+ defects | Failing |
Frequently Asked Questions
What is a dead pixel and how does it look on white?
A dead pixel appears as a black dot on a white or bright background. It's a pixel that has permanently failed and produces no light regardless of what the display is showing. Dead pixels cannot be fixed with software — they are permanent hardware defects. On a white screen, dead pixels are most visible because the contrast between a black dead pixel and the white background is maximum.
What is the dirty screen effect (DSE)?
The dirty screen effect appears as grey or off-white smudges, vertical bands, or haze on a white or light grey screen. It's caused by uneven distribution of the liquid crystal layer or backlight. DSE is common on budget VA panels and large IPS panels. It's most visible at medium brightness on light-colored content. Minor DSE is considered normal; severe DSE (visible during normal use) may qualify for warranty replacement.
How many dead pixels are acceptable on a white screen test?
ISO 13406-2 Class II allows up to 2 Type 2 defects (permanently dark pixels) per million pixels. A 1080p display has roughly 2 million pixels, allowing up to 4 dead pixels technically. However, most major manufacturers (Dell, LG, Samsung) offer 'pixel perfect' or zero-defect policies on premium monitors. A single dead pixel in the screen center is generally considered grounds for replacement within the warranty period.
Can I fix a dead pixel that shows on the white test?
Dead pixels (always dark) generally cannot be fixed by software because the subpixel transistor has permanently failed. Pixel-cycling software (JScreenFix, PixelHealer) has very low success rates on true dead pixels. However, what appears to be a dead pixel on the white test is sometimes a stuck pixel stuck in an 'off' state, which occasionally responds to pressure massage or pixel-cycling. Try cycling tools for 30 minutes before assuming permanent failure.
Is a slightly off-white tint on the white test normal?
Some off-white tint on a fresh white screen is expected from factory color temperature calibration — most monitors default to 6500K, which appears slightly warm (yellowish). A bluish-white appearance indicates a cooler color temperature setting. Uniform tinting across the full panel is normal. If the tint varies across the panel (e.g., one side is more yellow than the other), this indicates color uniformity issues which are panel defects.
Why do I see cloudy patches on the white test but not on other content?
Cloudy patches on solid white often indicate DSE (dirty screen effect) or backlight uniformity issues. These are most visible on flat, single-color content and nearly invisible on varied content like photos or video. Some level of uniformity variation is normal for all LCD panels. If the patches are distracting during normal desktop use (spreadsheets, document editing), that level of DSE may warrant a warranty claim.
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