Dead Pixel Checker

About Dead Pixel Checker

Dead Pixel Checker cycles bold solid colors — white, black, red, green, blue, magenta, yellow, cyan — across the full screen in fullscreen mode so faulty pixels become impossible to miss. Built for shoppers inspecting a new monitor inside the manufacturer's 7-30 day pixel-defect warranty window, IT teams qualifying batches of laptop and tablet displays, photographers checking color uniformity before a critical edit, gamers diagnosing burn-in or backlight bleed on OLED panels, and resellers grading used screens. Works on any fullscreen-capable device: phone, tablet, laptop, external monitor, even TVs via Chromecast. Adjustable auto-cycle speed (0.1-30 s per color — fast enough for a ~10 Hz stuck-pixel-fix flicker) makes hands-free panel inspection effortless, and a built-in Pass/Fail session report exports the tested colors, native resolution and timestamp as JSON for warranty claims. Renders on a canvas, fully offline-capable, zero data leaves your browser.

1. Enter fullscreen and ensure the room lighting lets you view the screen clearly.
2. Check white and black screens for dead (dark) or bright pixels that remain on.
3. Review red, green, blue, and secondary colors to catch stuck subpixels.
4. Note any defective areas for warranty claims or manual pixel fixing attempts.

How do I check my monitor for dead pixels with this tool?

Click Start, press F11 to enter fullscreen, then cycle through the solid-color test slides: pure red, pure green, pure blue, white, and black. On each color, lean within thirty centimeters of the panel and scan top-left to bottom-right in slow horizontal sweeps. Anything that breaks the uniform field is a defect: a black speck on white is a dead subpixel, a colored speck on black is a stuck subpixel, and a lit dot during the black slide is a hot pixel. Wipe the screen with a microfiber cloth first to rule out dust, and dim ambient lighting so reflections do not mask faults. Repeat at arm's length to gauge whether the defect is visible during normal use.

What is the difference between a dead pixel and a stuck pixel?

A dead pixel has lost power: all three of its red, green, and blue subpixels are dark, and it appears as a permanent black dot regardless of what the screen displays. The transistor driving it has failed and the defect is non-recoverable. A stuck pixel is the opposite: one or two of its subpixels are locked on at full brightness, producing a red, green, blue, yellow, magenta, or cyan dot that persists across every image. Stuck pixels can sometimes be revived by running a rapid color-cycle animation for an hour, gently massaging the spot through a microfiber cloth, or applying targeted pressure with a soft eraser. Dead pixels almost never recover and require panel replacement under warranty.

Why test for dead pixels right after buying a monitor?

Most manufacturers operate a dead-pixel warranty clock that starts the moment you accept delivery, with windows ranging from seven to thirty days. After that window, the standard ISO/IEC 9241-307 pixel-defect class still applies but the bar is far higher: a Class II panel may legally ship with up to two bright, two dark, and five subpixel defects per million pixels. Catching defects within the return window lets you exchange or refund the unit instead of arguing pixel counts with support. Run the full color sweep within a day of unboxing, photograph any defects you find against a ruler for scale, and contact the seller before the receipt date hits the seven-day mark.

What is backlight bleed and how do I detect it?

Backlight bleed is uneven LED light escaping around the edges or corners of an LCD panel because the polariser, light guide, or bezel pressure is not perfectly uniform. It only shows on dark content. Run the pure black slide in a completely dark room, let your eyes adapt for two minutes, then look for milky white or yellow clouds at the corners or pale glow strips along the edges. Some bleed is normal on IPS and VA panels; a manufacturer typically replaces a unit only if bleed exceeds roughly five percent of the screen area or forms distinct flashlighting cones. OLED panels do not have backlight bleed by design — every pixel is its own light source.

What pixel-defect class does ISO/IEC 9241-307 define for my monitor?

ISO/IEC 9241-307 defines four pixel-fault classes per million pixels of screen area. Class I permits zero bright, zero dark, and zero subpixel faults — premium and medical panels. Class II permits two bright pixels, two dark pixels, and five subpixel faults — the consumer default for most desktop monitors. Class III permits five bright, fifteen dark, and fifty subpixel faults — typical for budget displays. Class IV is the most lenient. A 4K UHD panel has roughly 8.3 million pixels, so a Class II 4K monitor may legally ship with sixteen bright defects and forty-one subpixel defects spread across the screen. Check the spec sheet or warranty page for your monitor's certified class before claiming a return.

Can a stuck pixel be fixed by running this tool?

Sometimes. Stuck subpixels happen when the liquid-crystal molecules above a transistor jam in one orientation. Rapidly flickering through saturated red, green, blue, white, and black at 5 to 10 Hz for thirty to sixty minutes can unstick the molecules by repeatedly twisting them through their full range. Use the auto-cycle mode in this tool, set the dwell time to 100 ms or less, and let it run unattended on the affected region. Combine with very gentle finger pressure through a microfiber cloth directly on the stuck pixel for ten to twenty seconds at a time. Success rates hover around 30 to 60 percent for fresh stuck pixels and drop to nearly zero after the pixel has been stuck for more than a few months.

Does this tool work on OLED, mini-LED, and laptop displays?

Yes for detection on every panel type, with caveats. On OLED and AMOLED phones and laptops, prolonged static color tests can cause temporary image retention — limit each color slide to under ten minutes and never leave the same slide running for hours. OLEDs almost never develop classic dead pixels but can show emitter failures appearing as black dots; these require panel replacement. Mini-LED displays have thousands of local dimming zones, so backlight bleed is replaced by blooming — a halo of leakage around bright objects on dark backgrounds. Test blooming with a pure white text cursor on the pure black slide. Laptop touchscreens may have additional digitiser layers that occasionally trap dust between glass and panel, mimicking dead pixels.

Which browsers and devices support fullscreen testing?

True element fullscreen works in Chrome, Edge, Firefox, and desktop Safari, and on Android Chrome. The catch is iPhone Safari: iOS only allows fullscreen for video elements, not arbitrary page elements, so the canvas test slide cannot enter real fullscreen on an iPhone. When the tool detects that document.fullscreenEnabled is unavailable, it tells you so and instead runs as a maximized overlay covering the page. To get near-full coverage on an iPhone, rotate to landscape, scroll once to hide the address bar, or add the page to your Home Screen so it opens without browser chrome. On iPad and Android the element fullscreen API is available, so the experience matches the desktop. The tool needs a secure context (HTTPS) but requests no camera, microphone, sensor, or location permission of any kind.

How do I record which colors showed defects for a warranty claim?

Use the built-in session report. While inspecting each color in fullscreen, tap Pass if the field is uniform or Fail if you spot a dead, stuck, or hot pixel; the tool advances to the next color automatically and keeps a running tally. When finished, press Export report to download a timestamped JSON file listing every tested color, its hex value, your Pass/Fail verdict, the panel's native pixel resolution (screen width × height × device pixel ratio), and the ISO/IEC 9241-307 context. A human-readable summary also drops into the Status box so you can copy and paste it straight into a support ticket or return form. This turns a casual eyeball sweep into defensible, reproducible evidence — exactly what resellers grading used screens and IT teams qualifying batches need when disputing whether a panel is within the pixel-defect spec.

How private is browser-based pixel testing?

Completely private. This tool runs entirely client-side using standard HTML, CSS, and JavaScript; the test slides are solid colors painted onto a canvas and fullscreen uses the Fullscreen API built into every modern browser. No camera, microphone, motion sensor, or location permission is ever requested — a hardware tester has no reason to read your sensors, and this one does not. There is no telemetry, no upload, and no analytics call during the test, and the optional report is generated and downloaded locally without leaving your device. You can verify by opening the browser developer tools, switching to the Network tab, and confirming that no requests fire while you cycle through colors. The same code works fully offline once the page is cached, which is useful when you want to test a display in a store before purchase without leaking what model or store you are checking from.