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Dead Pixel Test

Inspect a display against eight exact solid sRGB CSS colors, using fullscreen, click, Space, or arrow navigation without uploads.

Privacy: your files never leave your device. All processing happens locally in your browser.

How to use

  1. 1.Clean only the outer display surface by the manufacturer's safe method, then select Start fullscreen test.
  2. 2.Inspect black, white, red, green, blue, cyan, magenta, and yellow; click, press Space, or use arrow keys to move.
  3. 3.Note stationary mismatches across several fields, exit fullscreen normally, and use manufacturer diagnostics before any repair decision.

About Dead Pixel Test

Dead Pixel Test fills one large panel with eight solid CSS colors so you can visually inspect a display for points that do not match the surrounding field. The sequence is black, white, red, full-channel green, blue, cyan, magenta, and yellow. Select Start fullscreen test to request a larger browser presentation, then click the panel, press Space, or use the arrow keys to move through the sequence. The progress line always names the current pattern, its position, and its exact hexadecimal sRGB CSS value.

The color values are explicit product data rather than approximate theme colors. Black is #000000, white is #ffffff, red is #ff0000, the full green channel is the CSS named color lime at #00ff00, blue is #0000ff, cyan is #00ffff, magenta is #ff00ff, and yellow is #ffff00. The fixture is checked against the W3C CSS Color specification and the MDN named-color reference. Tests require eight unique identifiers and values and independently assert the three single-channel primaries.

Different solid fields can make different visual mismatches easier to notice. A point that remains dark on white or on a primary field may not emit as expected, while a point that remains bright or shows an unexpected component can stand out on black or another channel combination. Move through every color and inspect several regions, including edges and corners. Clean obvious dust from the outer screen surface using the manufacturer's safe procedure before concluding that a stationary spot is inside the panel.

Fullscreen is only a browser request made from the Start button. A browser can deny it because of permissions, embedding, policy, platform limitations, or user settings. When that happens, the page reports the failure and the in-page panel continues to work. The tool does not force kiosk mode, hide operating-system controls, disable sleep, change brightness, alter display settings, or prevent the browser's normal Escape behavior.

The requested CSS color and the physical light emitted by a display are not guaranteed to be identical. Browser color management, operating-system profiles, HDR modes, panel gamut, scaling, subpixel layout, viewing angle, local dimming, image enhancement, burn-in protection, and hardware calibration can change appearance. The W3C specification defines the CSS color values; it does not certify the physical output of a particular monitor. This page therefore identifies the requested stimulus, not a measured color from the panel.

A visible mismatch is also not automatically a dead pixel. Dust, reflections, screen protectors, pressure marks, image retention, stuck subpixels, browser zoom artifacts, GPU output, cable faults, screenshots, or remote-display compression can produce different symptoms. A screenshot can help separate content-generation problems from physical panel problems only when interpreted carefully: a physical defect generally does not become part of a screenshot, while a rendering defect might. Manufacturer diagnostics and warranty policies remain the appropriate authority for repair or replacement decisions.

Do not apply pressure, tap, heat, rapidly flash the panel, install untrusted repair software, or follow a destructive pixel-fixing claim because of this visual check. The tool deliberately uses static fields and provides no rapid strobe, seizure-risk animation, force instruction, or promise of repair. If the display shows spreading damage, electrical symptoms, impact damage, or safety concerns, stop using it and follow qualified manufacturer guidance.

No screenshot, display identifier, color profile, observation, or navigation history is uploaded. The current pattern index exists only in the tab and resets on reload. The reliable contract is narrow: render eight documented CSS sRGB color values in a large focusable panel, support forward and backward wraparound, request fullscreen only after direct user action, and clearly separate a visual aid from hardware diagnosis or remediation.

Methodology & sources

Render an eight-row immutable fixture sourced from CSS Color 4: black #000000, white #ffffff, red #ff0000, lime #00ff00, blue #0000ff, cyan #00ffff, magenta #ff00ff, and yellow #ffff00. Apply the current value as the panel background, choose a readable black or white label color, and move the index by modular forward/backward navigation. Request fullscreen only from the Start action and preserve in-page operation on rejection. External golden tests assert every mapping plus row count, unique IDs and values, hexadecimal syntax, RGB primaries, and wraparound.

Frequently asked questions

Does a mismatched point prove that a pixel is dead?
No. Dust, reflections, scaling, rendering, image retention, stuck subpixels, panel processing, and hardware faults can look different. This is a visual aid only.
Why is the green pattern labeled #00ff00?
It uses the full green sRGB channel, which CSS names lime. The CSS named color green is the darker #008000 and is not the single-channel maximum used here.
What if fullscreen is denied?
The in-page panel still cycles through all eight patterns. Browser policy, platform support, or embedding can reject fullscreen requests.

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