Check for dead pixel

how to detect defective pixels on any screen

The Dead Pixel Finder is a browser-based tool that fills the entire screen with a single solid color to help detect defective pixels on any display. It cycles through nine carefully chosen colors using keyboard navigation, on-screen buttons, or touch gestures on mobile devices. The tool requires no installation and runs as a standalone HTML file in any modern browser without external dependencies.

What a dead pixel is and why colors matter

A dead pixel is a display element that no longer responds to electrical signals and remains permanently black regardless of the image shown on screen. A stuck pixel differs from a dead pixel because it stays locked on a single color — typically red, green, or blue — instead of turning off completely. Testing against multiple solid colors is the only reliable way to reveal both types of defects across all three RGB subpixel components.

The nine test colors

The tool cycles through nine colors chosen to isolate each primary, secondary, and neutral channel of the RGB display model.

Black (#000000) is the most important test screen because it reveals stuck pixels locked on any active color against a fully dark background.
White (#FFFFFF) reveals dead pixels as black dots and also exposes uniformity issues such as backlight bleeding around screen edges.
Red (#FF0000) isolates the red subpixel channel and reveals green or blue stuck subpixels that remain visible against the pure red surface.
Green (#00FF00) isolates the green subpixel channel, which is the most sensitive channel in the human visual system and the easiest to spot defects in.
Blue (#0000FF) isolates the blue subpixel channel and is particularly useful for detecting warm-colored stuck subpixels on LCD panels.
Cyan (#00FFFF) combines green and blue at full intensity and reveals stuck red subpixels that appear as isolated dark-red dots on screen.
Magenta (#FF00FF) combines red and blue at full intensity and reveals stuck green subpixels as isolated green dots on the screen surface.
Yellow (#FFFF00) combines red and green at full intensity and reveals stuck blue subpixels as isolated blue or dark dots on screen.
Grey (#808080) exposes uniformity defects and brightness inconsistencies across the display surface that are invisible on fully saturated colors.

Navigating between colors

Three navigation methods are available and can be used simultaneously depending on the device and user preference.

The Previous and Next buttons in the control panel cycle backward and forward through the nine colors in the predefined sequence. The keyboard arrow keys (← and →) and the spacebar perform the same navigation without requiring the user to move their hand to the panel. On touch devices, a horizontal swipe gesture of more than 50 pixels triggers the next or previous color depending on the swipe direction. Clicking directly on the background area also advances to the next color, which allows one-click cycling without targeting any specific button.

The draggable control panel

The control panel is a floating overlay positioned in the top-left corner of the screen by default. It can be dragged to any position on the screen by clicking and holding on its header or any non-button area of the panel. The panel stays within the visible viewport boundaries during dragging, preventing it from being accidentally moved off screen.

The current color name and hex value are displayed in a dedicated info box inside the panel at all times during navigation. A brief color name indicator also appears at the center of the screen for one second whenever the color changes, then fades out automatically. The panel can be hidden or shown at any time by clicking the “Hide controls” button or by pressing the H key on the keyboard.

Full-screen mode

The full-screen button expands the browser window to cover the entire display, including the taskbar and browser chrome. This mode is essential for testing because even a one-pixel gap between the colored area and the screen edge can hide defects near the corners. Pressing the F key toggles full screen without requiring the user to reach for the on-screen button during inspection.

Full-screen mode combined with hidden controls provides the cleanest possible test surface for pixel inspection. The browser’s native Fullscreen API is used for this feature, which is supported by all major modern browsers on desktop and mobile. Exiting full screen restores the browser interface without interrupting the current color or resetting the navigation position.

How to perform an effective dead pixel test

Testing each color in a dark room significantly improves the visibility of defective pixels, especially for the black and dark-grey screens. The user should move their gaze slowly across the entire screen surface without focusing on a single area, which reduces contrast fatigue. Any point that does not match the background color — whether brighter, darker, or differently colored — should be noted and retested on adjacent colors.

A defect visible only on black or white screens is typically a dead or stuck pixel locked in its off or on state. A defect visible only on red, green, or blue screens indicates a stuck subpixel rather than a fully dead pixel element. A defect visible on multiple color screens that changes appearance between tests may indicate a cluster of adjacent subpixel faults.

Mobile and tablet support

The tool is fully functional on smartphones and tablets without requiring any adaptation of the test procedure. Touch swipe navigation replaces the keyboard shortcuts on mobile, and the control panel remains accessible at all times unless explicitly hidden. The full-screen API is supported on most mobile browsers, including Chrome for Android and Safari on iOS 16 and later.

The viewport meta tag ensures that the colored area fills the entire physical screen without any scaling or margin artifacts on mobile displays. Testing on mobile is particularly relevant for OLED screens, where dead or stuck pixels are more common than on traditional LCD panels due to organic material degradation. Performing the test at maximum screen brightness ensures that all subpixel defects are visible at their highest contrast against each test color.