White screen
Turn your screen completely white, instantly. No sign-up, nothing to install.
Simulated dimming — browsers can't raise a panel's backlight.
Screen colours
Quick links to a dedicated page for each colour.
More display tests
The rest of the suite, one click away.
Stuck Pixel Test
Cycle through RGB to spot pixels lit the wrong colour.
Backlight Bleed Test
A very dark field to spot light leaking from the edges.
Contrast Test
A stepped greyscale ramp to check separation near black and white.
Gradient Test
A smooth black-to-white ramp — watch for visible banding.
Colour Test
RGB, grayscale and primary hues in one place.
Brightness Test
A dimmable white field for comparing brightness across a display.
Ghosting Test
A moving block — watch for trailing behind the edges.
Refresh Rate Test
An in-browser estimate of on-screen frame timing.
Resolution Test
Viewport size, device pixel ratio and colour gamut.
Why use a white screen?
A flat white field is the fastest way to see what a panel is doing wrong. Dust and smears show up under an even wash of light; stuck pixels stand out as coloured dots; a cheap panel's corners go warm or grey. It also works as a soft light — for a video call, a photo fill, or finding something behind a desk.
Read the full guide →Common questions
Is this actually free?+
Yes. The core tool needs no account, no login and no payment. The site is supported by unobtrusive ads placed below the tool, never on top of it.
Can this fix a stuck or dead pixel?+
No. It cycles colours so a stuck or dead pixel becomes visible against a solid field — it does not repair the panel.
Does the brightness slider change my display hardware brightness?+
No — it applies a visual dimming overlay inside the browser. Actual hardware brightness is controlled by your device, not a webpage.
Do you store anything about me?+
No personal data is required to use the tool. See the Privacy page for details on analytics and any local storage used for preferences.