Screen Tester: Dead Pixels, Refresh Rate and Motion Blur
Guide & FAQFill the whole screen with one solid color at a time and look for dots that do not match: dead pixels stay black on bright colors, stuck pixels stay lit in one color on black, and hot pixels stay white.
Controls in the test: click, Space or the right arrow = next color. Left arrow or Backspace = previous. Keys 1 to 9 jump to a color. Esc = exit. Clean the screen first: dust and smudges look like pixels.
The page measures how often the browser can draw a new frame. Keep this tab in the foreground, plug in a laptop and close heavy apps. If you see 60 Hz on a 144 Hz monitor, set the refresh rate in your system display settings and check that the cable and port support it. Variable-refresh displays can show values that move around.
Follow the moving ship with your eyes, not the background. Blur trails behind the ship, dark or bright halos, and smearing on the lower lanes are signs of slow pixel response. Each lane uses different colors because pixels respond at different speeds depending on the color change. Try 960 px/s first, then faster. Take a photo with your phone at the same speed to compare screens.
Backlight bleed and clouding show as bright patches along the edges or corners of a dark picture. Dim the room, turn the screen brightness to normal or high, wait a minute for your eyes to adapt and look from straight on.
In the test, pressing Space or clicking switches between pure black and two very dark grays, which show uneven lighting (clouding) better. Left arrow goes back, Esc exits. A little glow when looking from an angle is normal on IPS panels (IPS glow); bleed that you see from straight on is the defect.
A good screen shows a smooth ramp with no visible stripes and no color tint in the gray ramp. Stripes in the smooth view mean the panel or the graphics settings are limiting color depth. The dark ramp is where most screens show problems. Compare with Dither switched on: if stripes vanish, your screen is fine and the bands come from 8-bit steps.
8 px: The quick brown fox jumps over the lazy dog 0123456789
10 px: The quick brown fox jumps over the lazy dog 0123456789
12 px: The quick brown fox jumps over the lazy dog 0123456789
14 px: The quick brown fox jumps over the lazy dog 0123456789
18 px: The quick brown fox jumps over the lazy dog
28 px: Sphinx of black quartz, judge my vow
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At 100 percent browser zoom on a screen running at its native resolution, 12 px text should have clean, evenly spaced strokes and the 1 px patterns should look crisp and even, without gray smearing or moire. Blurry text usually means the screen is not at native resolution, scaling is set to a fractional value, or the cable or monitor is applying sharpness or image scaling. Colored fringes on text are normal with subpixel text rendering but can look strong on some panel layouts.
Guide: Screen Tester: Dead Pixels, Refresh Rate and Motion Blur
Dead and stuck pixel test
Start the full-screen test and move through black, white, red, green, blue, cyan, magenta, yellow and gray. Use a click, Space or the arrow keys to switch colors, and Esc to leave. Look slowly at every part of the screen on each color. Defects that show on only one or two colors are usually stuck sub-pixels.
Refresh rate
The refresh tab counts how many frames your browser can draw every second and shows the current, average and typical display mode, frame time, the longest frame and the number of dropped frames. A steady graph means smooth output; red bars are frames that took noticeably longer than normal.
Motion blur and ghosting
Four lanes carry an original saucer-shaped object and moving text over light, dark and colored backgrounds. Change the speed from slow to very fast and look for trails and halos behind the objects. This shows how well the pixels keep up and whether overdrive settings are too weak or too strong.
Backlight bleed
In a dim room, the black screen reveals bright patches at the edges and corners. Two near-black grays help you notice uneven lighting.
Banding
The gradient ramps reveal color-depth problems. A smooth screen shows no stripes. Switch on dithering to separate panel limits from 8-bit steps.
Text sharpness
Text samples in several sizes and colors plus 1 px line patterns show whether scaling, cable or sharpness settings blur the picture.
- Use the monitor's native resolution and 100 percent browser zoom.
- Let the screen warm up for ten minutes before judging brightness or bleed.
- Turn off game mode filters and sharpening for a neutral result.
FAQ
How do I check my screen for dead or stuck pixels?
Open the Dead pixels tab, start the full-screen test and step through the colors with a click or the Space key. On white, red, green and blue look for dark or wrongly colored dots. On black look for any dot that stays lit. Clean the screen first and check from close up, because dust and fingerprints look like pixels.
What is the difference between a dead pixel and a stuck pixel?
A dead pixel never lights and shows as a black dot on bright colors. A stuck pixel is always on in one color and is easiest to see on a black screen. A hot pixel is stuck on white. Dead pixels cannot be repaired, stuck pixels sometimes recover. Check the maker's pixel policy, which often allows a few defects before a replacement.
Why does the refresh rate test show 60 Hz on my 144 Hz monitor?
The browser can only draw as fast as your system sends frames. In Windows, open Display settings, Advanced display and choose the higher refresh rate. Also check you use a cable and port that support it (DisplayPort or HDMI 2.0 and newer) and that the tab is in the foreground. Laptops on battery saver may lock the rate to 60 Hz.
How do I read the motion blur and ghosting test?
Pick a speed and follow the moving ship with your eyes. Fast, clean pixels keep the ship sharp. Blur behind it, dark or bright halos or color trails mean slow pixel response or aggressive overdrive. The four lanes use different color changes because some transitions are slower than others. For a fair comparison between monitors, use the same speed and viewing distance.
What is backlight bleed and is it normal?
Backlight bleed is light leaking around the edges of an LCD panel, visible on a dark screen in a dark room. A small amount is common. Judge it from straight on at normal brightness. Glow that appears only when you look from an angle is IPS glow, a separate and normal effect.
Does this tool upload anything?
No. All patterns are drawn in your browser. Nothing is sent anywhere and no sign-up or installation is needed.