How this test works
The page fills its backdrop with #808080: red, green and blue are each set to 128 out of 255. That gives you a neutral grey test value without a picture to distract from differences across the screen. Look from your usual viewing position for blotches, narrow bands or a tint that varies from one area to another. These patterns can be easier to notice on grey than on a white field, but their visibility depends on the panel and its settings.
Press Go full-screen grey to open the field. The browser's Fullscreen API is used where available; if the request is refused or unsupported, a fixed overlay fills the browser viewport instead. Tap the field or move the pointer to reveal the faded ✕ button, then use it to close the field. Esc also closes it. When browser fullscreen is active, leaving through the browser's own exit control closes the overlay too.
The readout shows the hex value, browser-reported screen and viewport sizes in CSS pixels, and fullscreen state. All are read locally, with nothing sent anywhere. It does not measure the light leaving the display. Room lighting, viewing angle and display settings affect what you see, so compare a suspect patch from your normal viewing position and check whether it also appears in everyday content. Use the dead pixel test for individual dots.
Frequently asked questions
What is a grey screen test used for?
Use it to look for differences in brightness or colour across the panel. Blotchy areas are often described as dirty screen effect or mura, while stripes may appear as horizontal or vertical banding. A plain background removes picture detail that could hide those differences. Look again in ordinary content, such as a camera pan across a football pitch, to see whether the same pattern is noticeable.
Is this the same as the dead pixel test?
No. Grey is useful for broad patches and tint, while the dead pixel test lets you compare individual dots on several backgrounds. Red, green and blue fields isolate the colour channels: a dot that stays dark on red but looks normal on green and blue suggests a red-subpixel problem. Grey uses all three channels together, so it can show a suspect dot without identifying which channel is involved.
Does #808080 mean half the brightness of white?
No. Each channel is 128 out of 255, near the middle of the encoded sRGB range, but that range is not linear in light. Applying the sRGB transfer function gives about 21.6 percent of reference white's relative luminance, not 50 percent. That is an encoding reference, not a reading from your display. Its actual light output depends on calibration, brightness controls and display processing.
Why does my grey screen look pink, green or blue?
Check night-light or blue-light filters, the active colour profile and the monitor's warm or cinema preset first. These settings can tint a nominally neutral grey. Room lighting and the panel itself can also affect its appearance. Compare again after changing one setting at a time. A second display in the same room can help you see a difference, but it is not automatically a neutral reference.
Is a static grey screen safe for my display?
Keep the check brief, use a comfortable brightness and follow your display manufacturer's guidance for static images. Long periods of unchanged content can contribute to image retention or wear, particularly on OLED; LCDs can also show temporary image retention. Do not leave the field running overnight. The grey background stays on one colour, with no automatic flashing or cycling.
