Fullscreen color fills to expose stuck pixels, dead pixels and bleed
Tap the screen (or press → / Space) to advance through all 10 test patterns; press Esc or tap ✕ to exit. Keep your eyes 30–50 cm from the display and look for dots that stay the wrong color on every fill.
A dead pixel is a sub-pixel whose transistor has failed: it stays pure black on every color fill, including white. It never lights up and cannot be fixed by software. A stuck pixel still receives power but is frozen on one color — typically red, green or blue. It shows as a bright colored dot on the black fill but vanishes (blends in) on a fill of its own color. Run the black fill first: any colored dot you see there is a stuck pixel, and any dot that stays black through the white fill is a true dead pixel.
The gray fills at 25%, 50% and 75% exist to catch subtler faults. Fine shading reveals dirty screen effect (uneven panel coating that smudges uniform grays), faint half-dead sub-pixels that only misbehave at mid-brightness, and pressure marks behind the panel. The uniformity grid checks that cell brightness is even across the whole display, and the gradient makes banding obvious — healthy panels fade smoothly, faulty ones show visible stripes.
Can I fix a stuck pixel? Sometimes. Rapidly cycling colors can jolt a stuck sub-pixel back into sync — run the auto cycle for 10–20 minutes with the problem area in view (keep the screen awake and the device plugged in). Success is not guaranteed and it never works on true dead pixels, which need panel repair or replacement.
How many dead pixels is "acceptable"? Most manufacturers' warranty policies tolerate a small number (often 3–5) before they'll replace a panel, and ISO 9241/Class definitions vary by panel density. If you just bought the device, photograph each faulty pixel against the test fills — retailers are usually far more lenient than the manufacturer policy within the return window.