Backlight bleed and uniformity test
Inspect bright edges, cloudy patches and uneven tones with fullscreen black, gray and white test fields. On an IPS LCD, a glow that changes as you move your head or viewing distance can be a panel characteristic. Keep a comfortable, ordinary monitor brightness and inspect the screen from your usual position.
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Test setup
Screen preview
Ready. Choose a pattern or enter fullscreen to inspect the display.
Black
Visual inspection only. The browser cannot see or count physical pixel defects.
- Browser test area (CSS pixels)
- Browser pixel ratio
Sources
- EIZO — monitor test patterns and visual inspectionSources reviewed: 2026-10-31
- MDN — fullscreen browser behaviorSources reviewed: 2026-10-31
- Dell — distinguish IPS glow and light leakageSources reviewed: 2026-10-31
- LG Display — self-emissive OLED panelsSources reviewed: 2026-10-31
- VESA — global and local LCD dimmingSources reviewed: 2026-10-31
- MDN — CSS pixels and browser scalingSources reviewed: 2026-10-31
How it works
- Inspect black at your normal viewing position.
- Compare several neutral gray and white fields.
- Hide controls and move the pointer out of the pattern.
Assumptions and limitations
Backlight bleed applies to backlit LCD panels; OLED pixels emit their own light. All observations here are visual. Room lighting, viewing angle, brightness, HDR and local dimming can change the appearance. The page cannot measure luminance, color accuracy or defect severity.
How to use this tool
Use consistent viewing conditions
Keep a comfortable, ordinary monitor brightness and inspect the screen from your usual position. Compare patterns with the same room lighting and picture settings. A completely dark room or exaggerated brightness can change how conspicuous an issue looks. Hide controls and move the pointer away before judging a black field, particularly when local dimming is active.
Distinguish glow from leakage
On an IPS LCD, a glow that changes as you move your head or viewing distance can be a panel characteristic. More fixed bright edges or patches may have another cause. These observations help describe what you see; they do not establish a diagnosis. Compare normal content and the manufacturer's built-in test before drawing a conclusion.
Inspect more than black
Gray and white fields can make broad changes in tone, tint or brightness easier to compare. OLED has no separate backlight, so use these fields for uniformity rather than calling an irregularity backlight bleed. The selected gray is a pattern value, not a calibrated brightness level. Browser color processing and display settings still influence its appearance.
Worked examples
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Compare a bright corner from two positions
Show black at your usual brightness. Look straight at the screen, then move your head slightly sideways and watch the same corner. Return to the first position and display gray to check whether the unevenness is visible there too.
Record whether the glow changes with viewing angle
Frequently asked questions
Does an even black screen prove there is no problem?
No. Local or global dimming can reduce backlight output on dark content. A pointer or visible control can change illuminated zones. Compare gray, white and ordinary content as well as black.
Does this control or measure monitor brightness?
The page changes image colors, not the monitor's hardware brightness. It does not measure nits, contrast or color error. Adjust the monitor through its own controls and compare observations consistently.
Processing and privacy
The calculation or transformation runs in your browser. The tool does not send its input values or generated output to an application server. Loading a page still makes infrastructure requests; optional analytics and Google consent messages have separate controls.
Privacy Policy. Privacy & preferences in the footer controls optional analytics.
Help and feedback
Consult the linked sources for definitions and reference data. Contact Support if you have a question or notice a problem.
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