Dead & stuck pixels
Nine pure colors, edge to edge. A dead pixel stays black, a stuck one stays lit.
1 minGuide
Monitor Sharpness Test
1 px grids, checkerboards, circles and fine text for scaling, overscan and aspect ratio. 100% in your browser - nothing is uploaded.
1 min4 patterns
Click the preview to run it full screen
Your display
Updates when you move the window to another screen- Resolution
- ---
- device px
- Pixel ratio
- ---
- devicePixelRatio
- Refresh rate
- ---
- measured in this browser
- Color gamut
- ---
- reported by the browser
- HDR
- ---
- standard range
- Orientation
- ---
- current
How to run the monitor sharpness test
01Use the native resolution
Set the operating system to the panel’s native resolution, with monitor scaling off.
02Check all four edges
Each edge of the grid must show a thin white line. A missing one means overscan.
03Look at the fine lines
The 1 px gratings and the checkerboard should stay crisp, not grey, wavy or haloed.
04Check the circles
The big circle must touch its square on all four sides and look round.
05Read the small text
The smallest line should be as sharp in every corner as in the center.
What to look for
- A white line on every edge. A missing edge means the picture is cropped (overscan).
- Gratings and checkerboard as fine, even lines. Grey mush, moiré or waves mean scaling.
- Bright or dark halos along lines: the monitor’s sharpness setting is too high.
- Round circles. Ovals mean the picture is stretched to a different aspect ratio.
- Small text as sharp in the corners as in the center, the first place projectors and TVs lose focus.
What counts as a defect
- At native resolution with scaling off, a monitor should show every 1 px pattern cleanly. Blur there is a fault or a picture setting.
- Grey or moiré patterns at a non-native resolution are expected: the image is being resampled.
- On a Mac in a scaled “looks like” resolution the pixel grid is larger than the panel’s, so 1 px patterns blur even on a perfect screen.
- Colored fringes on text are font smoothing, not a panel fault. They are stronger on QD-OLED and WOLED subpixel layouts.
What to do next
- TV or projector: turn on Just Scan, Screen Fit or 1:1 pixel mode, pick PC or Game mode and set sharpness to 0 or neutral.
- Monitor: reset sharpness to the default, often 50 or the middle step, and check the halos again.
- Stretched circles: set the graphics driver scaling to no scaling or keep aspect ratio.
- Fringed text on Windows: run the ClearType Text Tuner and pick the sample that looks cleanest.
Other screen tests
Each one checks a different part of the panel. The guided check runs them all in order.
Uniformity & clouding
Flat greys and white show clouding, dirty-screen effect and tinted zones.
1 minGuide
Banding & gradients
256 equal steps per ramp. A good panel shows them evenly, a weak one clumps them.
1 minGuide
Refresh rate & tearing
Measures the real frame rate in this browser and shows tearing on a moving bar.
30 sGuide
About the monitor sharpness test
A sharp picture needs every pixel of the signal to land on exactly one pixel of the panel. Wrong resolution, scaling, a TV’s overscan or an oversharpened picture mode all break that, and 1 px patterns show it at once: crisp lines turn grey, shimmer with moiré or grow halos. The patterns are drawn on your device pixels, so Windows scaling and browser zoom do not blur them.
It is one of the tests in the Screen & Monitor Test, which also runs a guided check through every test and ends in an inspection reportfor a return or RMA. Every pattern is drawn on your screen's own pixel grid, 100% in your browser - no upload, no install, no account needed.
Frequently Asked Questions
Overscan is a TV habit from broadcast days: the picture is enlarged a little and the edges are cut off. On a computer it hides the taskbar edge and blurs everything by rescaling. Look for Just Scan, Screen Fit, Full Pixel or 1:1 in the TV’s picture size menu, or the overscan slider in the graphics driver.
Because the signal is being rescaled before it reaches the panel: a non-native resolution, GPU or monitor scaling, a TV picture size mode, or a Mac scaled resolution. At native resolution with no scaling each line lands on one row of pixels and stays sharp.
Subpixel font smoothing (ClearType on Windows) sharpens text by lighting individual red, green and blue subpixels, assuming they sit in a straight RGB row. Panels with other layouts, like QD-OLED and WOLED, show those tricks as color fringes. Tuning ClearType or switching to greyscale smoothing reduces them.
Safari on iPhone does not allow web pages to go truly full screen. The test fills the whole visible area and hides all controls instead; rotate to landscape, or add the page to your Home Screen, to get the most of the panel in view. iPad and Android support real full screen.
No. Every pattern is drawn locally in your browser, and the inspection report is built and downloaded on your device. Nothing about your screen or your results leaves the browser, and no account is needed.
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