Category · 19 tools
Display Diagnostics
Find out what is wrong with a panel, from dead and stuck pixels to backlight bleed, burn-in and uneven brightness, using the screen you are reading this on.
Pixels and backlight
Single fields that each reveal one kind of panel fault.
- Dead Pixel TestSolid colors, full screen, changed only when you click or press a key.FindsDead pixels · stuck pixels
- Backlight Bleed TestDark room#000000A black full screen for spotting light that leaks in at the edges and corners.FindsCorner glow · edge light leaks
- Screen Uniformity Test#808080A gray field at three levels, with an optional grid for comparing zones.FindsBrightness falloff · tint drift · clouding
- OLED Burn-In TestOLED onlySolid fields that show retained images and uneven wear on OLED panels.FindsRetained images · uneven wear
- Screen Flicker (PWM) TestSteady fields for checking backlight flicker through your phone camera. Nothing flashes.FindsBacklight flicker, seen through a camera
Stuck pixels
Something to try on a stuck pixel. It flashes, so it opens only after a seizure warning.
- Stuck Pixel FixerFlashesA small flashing square you place over a stuck pixel, behind a seizure warning. No guarantee.Read first
Rapid flashing can trigger seizures in people with photosensitive epilepsy. The tool shows a warning and will not start until you accept it.
Picture quality
Patterns for contrast, gamma, color and sharpness.
- Screen Contrast TestNear-black and near-white steps that show whether shadows and highlights stay visible.FindsLost shadow and highlight steps
- Viewing Angle TestLarge color and gray blocks to watch as you move off-center.FindsColor and contrast shift off-center
- Gamma TestLine patterns beside gray patches for an approximate gamma reading.FindsApproximate gamma
- Color Accuracy TestStandard test colors to compare against a trusted reference.FindsVisible color differences
- Calibration Pattern (SMPTE bars)Color bars at 75% level for a quick setup check.FindsObvious color and level errors
- Color Banding / Gradient TestSmooth gradients that show visible steps or bands.FindsBanding · posterization
- HDR TestHDR displayShows what your browser reports about HDR support.FindsReported HDR support
- Sharpness / Text Clarity TestFine line patterns and small text that show halos, shimmer and blur.FindsHalos · shimmer · scaling blur
Motion and timing
Moving tests and estimates. They start only when you press Start.
- Refresh Rate TestEstimates the rate your browser draws frames at, and counts frames that take too long.FindsBrowser frame rate · long frames
- Motion Blur / UFO TestA small moving object for judging blur and ghosting at a chosen speed.FindsMotion blur · ghosting
- Screen Tearing TestOne moving bar that shows a break when frames tear.FindsScreen tearing
- Input Lag TestReaction trials that estimate the whole delay, from screen to you.FindsTotal response delay (estimate)
Guides for these tools
What a result means, and what to do next.
- Pillar guideHow to Test a MonitorA six-field monitor test you can run in your browser: which field to show first, why the order matters, and what to do when a field turns something up.
- ExplainerDead Pixel vs Stuck PixelWhat makers mean by a dark pixel and a bright one, how to tell the two apart in a couple of minutes, and how to rule out dust before you contact support.
- ReferenceDead Pixel Warranty PoliciesWhat Dell, ASUS, LG and Apple publish about pixel faults, quoted with the date each policy was read, and what that means before you return a screen.
- ExplainerHow to Fix a Stuck PixelMake sure it is a stuck pixel, then see what makers say about home fixes, why not to press on the screen, what a pixel-cycling tool can do, and the warranty.
- ExplainerIs Backlight Bleed Normal?Backlight bleed on an LCD, in the makers' own words: why it happens, the lighting Dell and ASUS judge it under, and when yours is worth returning.
- ExplainerOLED Burn-In: Detect and PreventImage retention versus burn-in on an OLED, how to check your own panel, and the protection features makers build in, quoted from their own support pages.
- ReferenceMonitor Buying GuideWhat monitor specifications promise, which ones a browser can check after delivery, and how to use the return window. No models, no prices, no affiliate links.
- ExplainerRefresh Rate ExplainedWhat refresh rate actually changes, how it relates to frame rate, blur, tearing and input lag, and which parts of the chain a browser can and cannot show you.
- Pillar guideHow to Calibrate a MonitorAn honest guide to adjusting a display by eye with test patterns, what that achieves, and the point where real calibration needs a measuring device.
- ExplainerHDR ExplainedDisplayHDR 400 against 600 and True Black, quoted from VESA's own published requirements, and what a browser can honestly tell you about your own screen.
- ExplainerScreen Flicker and PWMWhy some screens flicker at low brightness, what PWM and DC dimming are, what "flicker-free" means, and how to check your own screen with a phone camera.
- ExplainerEye Strain: Settings That HelpScreen brightness, glare, distance, position, text size and breaks: what the American Optometric Association and other eye-care bodies recommend for screen use.