Monitor and dead pixel test
Comprehensive display tests for dead pixels, backlight bleed, color accuracy, and response time
Your display
All tests run fullscreen. For best results, test in a dark room and ensure your monitor has been on for 30 minutes. Press ESC or the exit button to leave any test.
Tests
Dead pixel detector
Cycle through solid color screens (red, green, blue, white, black) to identify dead or stuck pixels. Click anywhere to advance.
Stuck pixel fixer
A draggable box that rapidly flashes RGB colors at high frequency. Position it over stuck pixels to help unstick them.
Color uniformity / gradient test
Fullscreen gradients from black to white, plus individual R/G/B channels. Check for visible banding or uneven transitions.
Response time visual
A moving white rectangle on a black background at various speeds. Observe motion blur and ghosting characteristics.
Backlight bleed test
Pure black fullscreen display with adjustable brightness. Check for light leaking from monitor edges in a dark room.
Viewing angle test
Alternating gradient and checkerboard patterns with labeled color swatches to evaluate viewing angle consistency.
Monitor testing tips
- Run the dead pixel test first, it is the quickest way to identify defective pixels
- For backlight bleed testing, turn off all room lights and let your eyes adjust for 30 seconds
- Color uniformity issues are more visible on IPS panels viewed head-on; check at various angles
- Response time ghosting is easier to spot at higher motion speeds
- The stuck pixel fixer works best when run for at least 20 minutes on the affected area
About monitor testing
Dead pixels are permanently off (black on any color). Stuck pixels show a fixed color. Stuck pixels can sometimes be fixed with rapid color cycling; dead pixels cannot.
Light leaking from monitor edges is normal on LCD panels but varies in severity. IPS glow appears as silvery sheen at angles and is distinct from backlight bleed.
Visible steps in gradients indicate limited color depth or poor gamma calibration. 8-bit panels may show banding that 10-bit panels do not.
Ghosting and motion blur appear as trails behind moving objects. Faster panel response times (1-4ms) reduce this effect significantly.
This monitor test suite puts six fullscreen patterns on your screen, one per fault you might be hunting. The dead pixel test cycles pure red, green, blue, white and black so a subpixel stuck on or off is obvious against a flat field. The stuck pixel fixer drags a rapidly flashing RGB box over one spot for up to a set number of minutes. Gradient runs black to white and black to each primary to expose banding. Response time slides a white rectangle across black at four speeds. Backlight bleed shows near-black at 21 brightness steps, and viewing angle offers gradients, a checkerboard and labelled colour swatches.
Key facts about Monitor and dead pixel test
| Tests included | dead pixel, stuck pixel fixer, gradient uniformity, response time, backlight bleed, viewing angle |
|---|---|
| Dead pixel colours | #FF0000, #00FF00, #0000FF, #FFFFFF, #000000 — click or tap to advance |
| Stuck pixel box | draggable, flashes RGB per frame, runs on a timer you set in minutes |
| Gradient set | black to white, black to red, black to green, black to blue |
| Response-time speeds | 2, 5, 10 and 20 pixels per frame, moving right to left and back |
| Backlight brightness | 0 to 20, mapped to a grey level of 0 to 50 out of 255 |
| Viewing-angle patterns | gradients, checkerboard, and labelled colour swatches drawn on canvas |
| Display mode | every test calls requestFullscreen on the document element |
| Cursor | hidden automatically after three seconds without movement |
| Flashing-content warning | stuck pixel and response time ask for consent once per session before starting |
| Monitor data shown | screen.width, screen.height, colorDepth, devicePixelRatio and orientation |
| Export | JSON report listing the tests completed and the detected monitor info |
| Focused dead-pixel page | the same colour cycle runs on its own at /tool/dead-pixel-test/, with nine screens and an auto-advance timer |
What happens to your file
Everything happens as CSS and canvas drawing inside this tab. The patterns are generated locally, the fullscreen request goes to your own browser, and no image, measurement or report is uploaded. The only thing written outside memory is a single sessionStorage flag recording that you acknowledged the flashing-content warning, so the two strobe tests do not ask again in the same browsing session; it disappears when you close the tab. The monitor details in the report come from window.screen and devicePixelRatio, which any page can read, and the report itself is built as a Blob and downloaded by your browser without a network round trip.
About this tool
- 1
Warm the panel up first
Leave the monitor on for about thirty minutes before judging uniformity or bleed. A cold backlight and a warm one look different, and that difference is bigger than most faults you are looking for.
- 2
Start with dead pixels
Launch the dead pixel test and click through red, green, blue, white and black. A dot that stays black on every colour is dead; one that stays red, green or blue is a stuck subpixel; a dot that is only visible on white is usually dust on the panel.
- 3
Try the stuck pixel fixer
Drag the flashing box over the stuck pixel, set a duration in minutes and start it. Rapid colour cycling sometimes frees a subpixel that is jammed on. A truly dead pixel will never come back.
- 4
Check gradients for banding
Run the black-to-white gradient, then each primary. Smooth panels show a continuous ramp; visible steps indicate 6-bit-plus-dithering or an aggressive colour profile.
- 5
Watch motion at four speeds
In the response time test, step from 2 up to 20 pixels per frame. Trailing behind the moving rectangle is ghosting; a bright edge in front of it is overshoot from overdrive set too high.
- 6
Do backlight bleed in the dark
Turn the room lights off, open the backlight bleed test and leave brightness at 0. Light pooling in a corner is bleed; a lighter band along an edge is clouding. Raise the slider a step or two to see how much is hidden in normal use.
- 7
Finish with viewing angle
Switch between gradients, the checkerboard and the colour swatches while moving your head left, right, up and down. IPS panels shift least; VA panels darken off-axis; TN panels invert vertically.
| Fullscreen API | required — supported in Chrome, Edge, Firefox, Safari and Opera on desktop |
|---|---|
| iOS Safari | has no Fullscreen API for arbitrary elements, so tests run inside the browser chrome |
| Exit | press Escape or use the on-screen exit button; leaving fullscreen closes the test |
| Panel types | IPS, VA and TN show backlight bleed; OLED and QD-OLED have no backlight to bleed |
| Colour accuracy | patterns are sRGB hex values; the page cannot bypass your OS colour profile or night-light filter |
| Response time | a visual ghosting comparison, not a millisecond measurement |
| Multi-monitor | the test fills the screen holding the browser window — move the window to test a second display |
| Account or install | none — no signup, no download |
- Photograph a suspected dead pixel on the white and the black screen with the camera's exposure locked — retailers usually want evidence on both.
- Check your country's or manufacturer's dead-pixel policy before returning a panel; many only accept a return above a set number of faulty pixels.
- Clean the screen before you start. A speck of dust on black looks exactly like a stuck white subpixel.
- Run the stuck pixel fixer in sessions of ten to twenty minutes rather than one long run, and retest the dead pixel screens between sessions.
- Banding that appears only in a browser can come from the GPU's output colour depth or a video driver setting, not from the panel — check the display output format before blaming the monitor.
- OLED owners can skip the backlight bleed test entirely; those pixels emit their own light and there is no backlight behind them.
- Compare two monitors by moving the same browser window between them rather than opening two windows, so both see identical patterns.
- The flashing tests are deliberately gated behind a warning; skip them if you are sensitive to strobing content.
- Fullscreen dead pixel cycle in red, green, blue, white and black
- Draggable stuck-pixel fixer with a minute timer
- Four gradient ramps for banding and uniformity
- Response-time motion test at four speeds
- Backlight bleed screen with 21 brightness steps
- Viewing-angle gradients, checkerboard and colour swatches
- Completed-test tracker and JSON report export
- Inspecting a brand-new monitor for dead pixels while the return window is still open.
- Deciding between two panels by comparing backlight bleed in the same dark room.
- Checking a laptop screen for pressure marks and clouding before buying it second-hand.
- Trying to revive a stuck subpixel before starting a warranty claim.
- Judging whether a monitor's overdrive setting is causing overshoot on fast motion.
- Verifying uniformity on a screen used for photo or video work.
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