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.
Running this on a phone where the browser bar refuses to hide? Leave the "Test in full screen mode" box checked and tap a color tile - on devices that block the Fullscreen API the page falls back to a window-fill paint that still pushes the chosen color edge-to-edge across the visible canvas, so a stuck sub-pixel reads the same on a 6-inch handset as it does on a 27-inch monitor. Tap Reset (or use the back gesture) to return to the tile picker between colors; nothing is recorded between presses, so the next sweep is a deliberate choice.
Free Online Dead Pixel Test - Instantly Check Your LCD & OLED Screen Quality
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.
Wondering if your screen has dead pixels or other display issues? Use the free online dead pixel checker to quickly identify faulty pixels on LCD, OLED, or LED screens. The full-screen color test paints a solid red, green, blue, black, white, or yellow field across the entire viewport so dead, stuck, or discolored pixels stand out against a uniform background, and the three live readout numbers below the tiles let you verify the actual painted resolution without downloads.
One mobile-fullscreen workflow note for readers on a phone where the browser bar refuses to hide. The "Test in full screen mode" checkbox above invokes the OS Fullscreen API on tile click - on supported devices the browser chrome retracts so a stuck pixel in the top or bottom row of the panel is not masked by UI furniture. On managed phones where Fullscreen is policy-blocked the page falls back to a window-fill paint that still pushes the chosen color edge-to-edge across the visible canvas, so a stuck sub-pixel reads the same edge-pattern on a 6-inch handset as it does on a 27-inch desk monitor.
What the three resolution readouts mean. Under the color tiles the page lists three live numbers: your viewport, your screen resolution, and your native screen resolution (the resolution multiplied by window.devicePixelRatio). Confirm the native number matches your laptop or monitor spec sheet before flagging a suspect dot - 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.
Running a full pre-meeting hardware check? After the screen test, verify the rest of the input surface with the microphone test (level metering, permission check) and the camera test (resolution, preview). Together the three take under a minute and cover every hardware surface a typical video call depends on.
Going deeper on pixel defects? Read Dead pixel testing guide for the dead-vs-stuck-vs-hot taxonomy and the warranty-return threshold most manufacturers apply, and How to test for dead pixels before returning a monitor for the evidence pack (screenshots, pixel counts, test conditions) that speeds up an RMA.
Screen test passed today, but the laptop travels with you? Read Device test checklist for remote work for the schedule that catches new dead pixels, backlight bleed, or a loose display cable on a regular cadence rather than only at warranty-claim time. Pairs the screen check with mic, webcam, and keyboard tests in one 90-second sweep.
Spot key issues alongside the screen issues? Run a keyboard test to confirm every key registers - non-working keys are easier to surface in the same browser session as the screen check, and the keyboard test takes under thirty seconds.
Searched a different name for the same check? Read Screen / display test synonyms for what each name (screen test, display test, panel test, monitor test) actually covers, and What an LCD test does (and when to run one) for the underlying pixel check explained in plain terms - both pair with the colour cycle above so you know whether the right tool is open for the question you typed in.
Wondering whether to install a native app instead? Read Screen test online vs app - which is more accurate for the side-by-side: panel-level defects (dead pixels, uniformity, bleed) read the same in both; refresh-rate, 10-bit / HDR, and ICC color profile checks need a native app because the browser abstracts those signals away.
Searched for "test lcd" / "lcd tester" / "lcd test online" and not sure which tool fits your job? Read Test LCD: Pick the Right Screen-Test Tool - the disambiguation guide that maps each query phrasing to the right tool (panel pixels vs touch surface vs camera vs microphone) in one decision table.
Free, in your browser, with nothing uploaded. The LCD dead-pixel test is built around a single decision: render a perfectly uniform color across the entire viewport so the reader can spot defects by eye, without installing software or creating an account. No tile click leaves the browser, no still is captured, and the page does not record anything between presses. Closing the tab is the only cleanup the test needs.
Need the full device-check index? Go back to the Device Test Tools hub - the central page lists this LCD test, plus the camera test, keyboard test, and microphone test in the order that catches the most pre-meeting faults first. The hub is the place to land when the screen check passes but another layer (audio, lens, key registration) may still be at fault.
Why the "Test in full screen mode" box is ticked by default. Tick the full-screen checkbox before you start a sweep - the OS-level fullscreen mode hides browser chrome (address bar, tab strip, taskbar) so a stuck pixel sitting in the top or bottom row of the panel is not masked by UI furniture, and the test color reaches the actual edge of the display the panel manufacturer is responsible for. The box is preserved between sweeps, so once you tick it the next click on a color tile paints edge-to-edge again without re-ticking. On panels where the Fullscreen API is blocked by policy the page falls back to a window-fill paint that still pushes the chosen color across the visible canvas; the practical difference is only the centimetre of chrome at the top of the screen.
When to uncheck the "Test in full screen mode" box. The box is checked by default because a true fullscreen paint hides the browser chrome and lifts the test color edge-to-edge, which makes a stuck sub-pixel easier to catch at arm's length. Uncheck it in three situations: when you want the color tile and a second reference window (a spec sheet, a photo of the suspect dot) visible side-by-side without alt-tabbing; when you are on a kiosk or work laptop where the Fullscreen API is policy-blocked and the request silently fails; or when you want to repeat the same sweep quickly without pressing Escape between tiles. With the box unchecked, each tile click paints the page background instead of the whole display, and Reset returns you to the picker with one click.
Read the guide: LCD Screen Test
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
How does the dead pixel checker work?
The tool displays full-screen colors one by one to make dead pixels appear as black dots that don't change. Stuck pixels may stay on one color.
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.
Can I test both LCD and OLED screens?
Yes. This tool supports LCD, OLED, and LED displays, allowing you to test any screen.
Will this tool work on mobile devices?
Yes! The test works on both desktop and mobile devices. Just open the tool in your mobile browser to check your screen.
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 test work on OLED displays, and is OLED burn-in a dead pixel?
The test works on OLED - the solid-colour screens expose uniform-brightness issues the same way. OLED 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). 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.
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.
Is the test different on an OLED screen than on an LCD?
The same color cycle runs on OLED panels, but the failure modes shift: OLED pixels emit their own light, so the backlight-bleed check above cannot occur, and two OLED-specific defects (burn-in and image retention) become the checks worth watching for. 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.
Which tile catches which defect?
The six color tiles are not interchangeable - each one surfaces a different failure mode. Use the black tile to scan for backlight bleed (uneven glow at the panel edges, only meaningful on LCD - on OLED the pixel itself emits light, so true black is true off and bleed cannot occur). Use the red, green, and blue tiles to catch stuck sub-pixels at the native resolution number the page lists on load; a stuck red sub-pixel is invisible on the red field but jumps out on the green and blue ones. White and yellow round out the sweep for uniform-tint defects.