Omikuji Tools Text & Dev

Dead Pixel & Refresh Rate Test

Fill the screen with solid colors one after another to spot pixels that stay lit or stay dark. Measure your monitor's real refresh rate (Hz) and check resolution, HDR and other display details on the same page.

What this screen test does

  • Nine full-screen colors — black, white, red, green, blue, gray, cyan, magenta and yellow — to find dead, stuck and hot pixels and uneven backlight
  • Measures the refresh rate from a few seconds of frame timing and matches it to common rates (60, 120, 144, 165, 240 Hz…)
  • Extra tests: gradient banding, a 1-pixel grid, small text and a moving square for motion blur
  • Shows resolution, approximate physical pixels, viewport, pixel ratio, color depth, HDR support and color gamut (P3)

When to use it

A new monitor arrives

Check for dead pixels, stuck pixels and uneven backlight while the return window is still open.

Buying a used monitor or laptop

Check for dead pixels and the real refresh rate on the spot before you pay.

Gaming monitor setup

Confirm your 144 Hz or 240 Hz monitor really runs at that rate, and catch a wrong cable or OS setting.

Phone and tablet screens

After a screen replacement or on a second-hand device, check for dead pixels with full-screen colors.

Privacy

Display details and refresh rate results are only shown on this page and never sent anywhere. The browser only stores your light/dark theme setting.

FAQ

How many dead pixels are acceptable?

Because of how LCD and OLED panels are made, a very small number of pixel defects is often not treated as a fault. Whether you can get a replacement depends on the manufacturer's pixel policy for that model and on the seller's guarantee; some sellers offer a zero bright pixel guarantee. Check the conditions and time limit, and report it early with photos and the location of the pixel.

It says 60 Hz, but my monitor is 144 Hz. Why?

The usual causes are an OS display setting still at 60 Hz, a cable or port that cannot carry the higher rate (such as an older HDMI version), or a laptop limiting the rate on battery or in power-saving mode. Safari caps measurement at about 60 Hz by default, so measure again in Chrome or another browser. A background tab or a window on another monitor can also read lower, so bring this window to the front and press “Measure again”.

Full screen does not work. What can I do?

Some browsers, such as Safari on iPhone, cannot put a page into full screen, so the test fills the browser window instead (the address bar stays). Rotating the device to landscape or opening the page from the home screen gives you more area. On a computer you can also press F11 to make the whole browser full screen. Press Esc or “Exit” to finish.

Can a dead pixel be fixed?

A dead (always dark) pixel generally cannot be fixed. A stuck pixel occasionally recovers on its own, but there is no reliable fix. Avoid pressing hard on the screen or running intensely flashing videos for a long time — they can cause other damage or make you feel unwell. If the screen is still under warranty, contacting the seller or manufacturer is the safest route.

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Dead pixel check

Switch colors with ← →, a click or a swipe; press Esc to finish. The cursor and hints hide after a few seconds.

Start from a color

More tests

Refresh rate

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Estimated from how often the browser redraws the page. Safari (Mac, iPhone, iPad) caps animation at about 60 fps by default, so even a 120 Hz device reads 60 there — measure again in Chrome or another browser. Power-saving mode or battery power on laptops and background tabs also read lower, and variable refresh rate displays (ProMotion, FreeSync, G-SYNC) may read somewhat lower. With two monitors, it measures the screen this window is on. If a 144 Hz monitor shows 60, check the OS display settings and the cable (HDMI version or DisplayPort).

Display info

Screen resolution (CSS pixels)
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Approx. physical pixels
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Viewport
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Pixel ratio (devicePixelRatio)
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Color depth
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HDR
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Color gamut
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Orientation
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Resolution changes with OS scaling (125%, 150%, etc.) and browser zoom. Physical pixels are estimated as CSS pixels × pixel ratio. HDR and color gamut are what the browser and OS report.

If you find a dead pixel

Hot / stuck-on pixel
A dot that stays white, red, green or blue on a black screen. Very noticeable in dark scenes.
Dead pixel
A dot that stays black on white or bright colors. The pixel no longer lights up.
Stuck pixel
A dot that stays a different color from its surroundings as you switch colors (one of its red, green or blue sub-pixels is always on or always off). A sub-pixel that is always on shows up on black; one that is always off shows up on that color.
Dust or a pixel?
If it survives a wipe with a soft cloth and does not move when you change your viewing angle, it is a pixel defect.

Take photos (the whole screen and a close-up), note where it is, and contact the seller or manufacturer. How many defective pixels qualify for a replacement depends on each manufacturer's pixel policy and the seller's guarantee (some offer a zero bright pixel guarantee), and some only apply for a short time after delivery — so test as soon as your monitor arrives.

How to use

  1. Press “Start full screen” or one of the color buttons. The color fills the whole screen.
  2. Switch between black, white, red, green, blue… with ← →, a click or a swipe, and scan every corner for odd dots.
  3. Use the gradient, grid, text and motion tests to check banding, sharpness and motion blur. Press Esc to return.
  4. The refresh rate is measured automatically when the page opens. Turn off power saving and press “Measure again” for a reliable reading. Safari caps it at about 60 Hz by default, so use Chrome or another browser for high refresh rates.