A screen test, display test, monitor test, or dead pixel test - the same six full-screen colors below cover all four names; click a color to fill the viewport and look for stuck or discolored pixels.
This tool draws a single solid color across the full viewport so dead, stuck, and discolored pixels stand out against a uniform background. Cycle through red, green, blue, black, white, and yellow to cover all six diagnostic colors.
Free Online Dead Pixel Test - Instantly Check Your LCD & OLED Screen Quality
Last reviewed: 2026-06-25
Press any color tile above to start a full-screen color cycle - sweep red, green, blue, black, white, and yellow to spot stuck pixels, dead pixels, or backlight bleed. No install.
Also called a screen test, display test, panel test, or monitor test - the same full-screen color cycle covers all four names and works on LCD, OLED, and LED panels.
What each color reveals
Pick one tile at a time so each defect class has a chance to surface against the field that exposes it.
| Color field | What it reveals |
|---|---|
| Black | Stuck-bright pixels - a subpixel jammed on shows as a coloured dot against the dark field. |
| White | Dead-dark pixels and surface dust - a permanently off subpixel reads as a black speck, and a fleck of dust looks the same. |
| Red, green, blue | Subpixel defects in the matching channel - a defect in one channel only is invisible on the other two. |
| Yellow | Stresses both red and green subpixels at once - run it last to catch the partial dimming the single-channel fields miss. |
Tick the "Test in full screen mode" checkbox before clicking the first color tile so the browser chrome retracts and defect areas near the panel edges are not covered.
On phones and tablets
Tick the full-screen checkbox on a phone to let the colour paint edge-to-edge, where backlight bleed and stuck pixels most often appear. Android Chrome and Firefox enter true fullscreen on the tap; on iOS Safari, scroll once to retract the address bar or rotate to landscape as a fallback.
Reading the three resolution numbers
- Viewport - the area actually painted, after the browser chrome takes its share of the screen.
- Screen resolution - the resolution your operating system reports for the display.
- Native screen resolution - the screen resolution multiplied by
window.devicePixelRatio. On a hi-DPI panel a single CSS pixel hides several physical sub-pixels behind it, and a stuck sub-pixel can hide between them. Confirm the native number matches your monitor spec sheet before flagging a suspect dot.
Tell backlight bleed from a viewing-angle gradient
Run the black tile to tell the two apart: backlight bleed reads as a warm-grey wash that fades inward from the bezel, while a viewing-angle gradient inverts when you tilt the panel. Run white to confirm - a corner that still reads cooler at full brightness when the panel is square to the eye is real bleed worth a warranty conversation; a cast that disappears at that angle was the viewing angle.
Everything stays in your browser
No tile click leaves the browser, no image is captured, and no account is needed. Closing the tab is the only cleanup.
Pair with the full device check
Before a call, pair this with the microphone test (audio level metering), the camera test (live preview and resolution), and the keyboard test (key registration) - the four checks together take under two minutes and cover every input surface.
Checking the screen as part of a full device check
This page covers the display side of the check: each of the six color fields - black for stuck-bright pixels, white for dead-dark pixels and dust, red, green, and blue for single-channel subpixel faults, and yellow to stress red and green together - surfaces a different defect class, along with any backlight bleed or uneven brightness near the edges. Once the screen looks clean, many readers run a quick camera test and microphone test on the same device so every input surface is confirmed before a call.
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Read the guide: How to check a laptop screen for dead pixels and backlight bleed
Not sure whether your display is a true LCD or an LED-backlit panel? The guide LED test vs LCD test - which applies to your screen explains the panel differences and confirms whether this color-cycle test covers what your hardware needs.
Mobile fullscreen fallback - when the API does not engage
On mobile browsers the Fullscreen API is conservative: Safari on iOS does not grant true fullscreen to web pages, and some Android browsers require a user gesture inside the last few hundred milliseconds before the request succeeds. When the request does not engage, the page falls back to a windowed paint that fills the visible viewport but leaves the status bar and address bar visible. To extend the painted area, scroll down once to hide the address bar, then tap a color tile in the same gesture window; on iOS, rotating to landscape and adding the page to the home screen also widens the paint. The viewport readout reports the actual painted dimensions so you can confirm which mode is active.
Frequently Asked Questions
Does the test send any data anywhere?
No. The page only renders solid-color backgrounds inside your browser tab; nothing is captured, uploaded, or recorded between tile presses. Closing the tab is the only cleanup the test needs - no account, no install, no telemetry sent off the device.
What is the difference between a dead pixel and a stuck pixel?
A dead pixel is permanently black regardless of the colour field - the transistor has failed. A stuck pixel shows one colour (usually red, green, or blue) because one sub-pixel is permanently on. Dead pixels are usually grounds for a warranty return; stuck pixels sometimes respond to pixel-massage or colour-cycling techniques.
How many dead pixels do I need for a warranty return?
Policies vary by manufacturer. Premium monitors (Apple Studio Display, Dell UltraSharp) typically have a zero-defect guarantee. Budget panels often require three or more dead pixels within a specified region before accepting a return. See our guide on testing before return for the full list.
Can this tool fix stuck pixels?
The tool cannot fix pixels directly, but running the colour cycle rapidly for several hours can sometimes unstick a pixel by exercising the liquid crystal. Success rate is around 30-40% on stuck (not dead) pixels. For a guaranteed fix, warranty replacement is the reliable path.
Does this work on OLED, and what changes?
The same color cycle runs on OLED panels - the solid-colour screens expose uniform-brightness issues the same way. What shifts is the failure modes: OLED pixels emit their own light, so the backlight-bleed check above cannot occur on OLED, and two OLED-specific defects (burn-in and image retention) become the checks worth watching for. Burn-in is not a dead pixel: a burned-in pixel still changes colour, it simply drifts toward the image it retained longest (Slack sidebar, Chrome tab row, menu bar). Image retention is the temporary version of the same effect that fades after the panel displays other content. To spot burn-in, compare the grey and white screens against a phone camera held close - afterimages show up as faint patterns that follow your apps' UI chrome. Read OLED test vs LCD test: what changes on an OLED panel for which LCD-test checks still apply on OLED and how to read burn-in vs image retention.
Why do some "dead" pixels look alive on my Retina / high-DPI display?
A subpixel defect on a 4K or Retina panel is roughly one-third the size of a defect on a 1080p panel, so a sub-pixel that is permanently off appears as a faint colour tint rather than a dot. Zoom your browser to 200%+ during the test, and use a magnifier or phone camera at close range to confirm. A single-subpixel defect rarely qualifies for warranty return on its own; pair this test with the return workflow guide to build the evidence pack manufacturers ask for.