how it works

Check a display with controlled color fields.

A browser screen test is a way to make observations repeatable. It can expose a spot or uneven area against a simple background, but it cannot identify the cause or certify a panel.

What fullscreen actually does

When you choose Start, the page creates a color layer and asks the browser Fullscreen API to show that layer fullscreen. The permission prompt and browser rules remain in control. If the request is blocked or unsupported, the layer stays open only across the page viewport; browser bars, a camera cutout, rounded corners or operating-system overlays may remain visible. The tool does not change monitor brightness, calibration, resolution or hardware settings.

Choose the field for the observation

White

Useful for surface dust, fingerprints, darker points, broad tint and brightness variation. It cannot distinguish dirt from a dark pixel by itself, and glare can hide subtle variation.

Black

Useful for bright points, edge glow and light areas in a dark room. It cannot prove that glow is a fault: backlight design, local dimming, exposure and viewing angle all affect the result.

Red, green and blue

Useful for seeing whether a point behaves differently on one primary color channel. These fields do not identify the electrical cause, and color-management or sub-pixel layout can change what you perceive.

Gray

Useful for comparing neutral tone, banding and gradual uniformity changes without maximum brightness. It cannot replace a calibrated pattern, measurement instrument or manufacturer uniformity specification.

Warm white

Useful as a softer reading or illumination field and for comparing a warm neutral with pure white. It is an intentional cream color, not a color-temperature measurement or calibration reference.

Custom color and grid

A custom HEX field can repeat a troublesome UI color. The grid provides location cues for tiny marks, but its 24-pixel CSS spacing is not a map of physical panel pixels and browser scaling can change it.

A structured display-check workflow

Prepare: note normal brightness, browser zoom and display scaling. Power the display off before cleaning it with the method recommended for that panel.
Set conditions: return to normal brightness and reduce strong reflections. Start at your ordinary viewing distance and angle.
Scan consistently: open white, black, red, green, blue and gray in that order. Sweep the same path across the screen instead of staring at one point.
Recheck: if something stands out, close fullscreen, change only one condition—such as angle or ambient light—and repeat the same color.
Locate: enable the grid or use a custom color to find the spot again. Record the color and conditions in plain terms if you need to discuss it with a repairer or manufacturer.

Worked observations and confounders

A dark dot appears on white but seems to move when you change your head position. Clean the surface and repeat. Dust on the panel, dust on glasses, a reflection or viewing angle can shift relative to the displayed grid; a physical pixel location will remain fixed on the panel.

A bright patch appears near an edge only on black. Repeat at the same brightness from the centered viewing position, then compare in ordinary room light. Backlight construction, local dimming, camera exposure and off-axis viewing can exaggerate a dark-screen patch. The page cannot decide whether it is within a product specification.

Thin bands appear on gray. Reset browser zoom and keep operating-system scaling unchanged. Gradients introduced by the panel, color profile, browser compositing or viewing angle can look similar. A flat browser field is an observation aid, not a calibrated uniformity measurement.

Dead versus stuck pixels

“Dead” commonly describes a pixel that remains dark, while “stuck” commonly describes a pixel or sub-pixel that remains lit or fixed on a color. The visual boundary is not always clear on modern high-density displays: one sub-pixel is difficult to resolve, scaling can cover multiple physical pixels, and dirt can mimic either case. Check the same fixed location on black, white and each RGB field. Use the terms as descriptions, not a diagnosis; warranty definitions and pixel policies belong to the display manufacturer.

Mobile, accessibility and safe exit

Phone and tablet browsers may not grant element fullscreen, especially on some platforms or when the action is not treated as a direct tap. The viewport layer still works, but browser chrome, safe areas and automatic brightness may remain. Rotation or pinch zoom also changes the comparison, so keep orientation and zoom stable.

Every test opens from a labeled button, exposes a labeled Exit control, and can be closed with Esc where a keyboard is available. Clicking or tapping the empty field also exits. The color cycle changes every 1.6 seconds; avoid it if flashing or rapid color changes cause discomfort. The stylesheet honors the browser’s reduced-motion preference for nonessential motion, and you can use individual static presets instead of cycling.

Privacy and network boundary

Color selection, grid state and the open test layer are handled in the current page session. There is no account, result upload or server-side display analysis. Loading the site still makes ordinary requests to the web host and the configured font provider; those services can receive standard request information such as an IP address, timestamp and user agent. No advertising or audience-measurement runtime is currently loaded. See the privacy page for the exact boundary.

Return to the tool

Start with static fields, keep the conditions consistent, and describe only what you can reproduce. Open the White Screen Test