Check a display in two minutes — new monitor out of the box, second-hand laptop, or the panel you suspect grew a bright green dot. The fullscreen cycle walks solid colors that expose dead and stuck pixels, grays and gradients that reveal backlight clouding and banding, and single-pixel grids that show instantly whether the display is running at its native resolution.
The test is pure CSS running in your browser — nothing to install, works on phones and TVs too. While you are inspecting colors, the color blindness simulator shows how your designs look to color-blind users, the contrast checker validates text legibility, and the webcam test covers the camera above your screen.
Frequently asked questions
What is the difference between a dead pixel and a stuck pixel?
A dead pixel receives no power and stays black on every color — you spot it on the white screen. A stuck pixel has one or more subpixels jammed on, so it glows red, green, blue, or white against the black screen. The distinction matters: stuck pixels sometimes recover, dead ones essentially never do.
How do I check for dead pixels properly?
Run the fullscreen cycle in a dim room with the screen clean — dust looks exactly like a dead pixel. Scan slowly across each solid color, especially white, black, and the three primaries, and check the corners and edges where faults hide. A magnifier helps on high-DPI screens where a single pixel is tiny.
Can a stuck pixel be fixed?
Sometimes. Cycling rapidly between colors in the stuck area for a while, or a very gentle massage through a soft cloth on LCD panels, occasionally frees a stuck subpixel. There are no guarantees, and never press hard on any panel — especially OLED. If the screen is under warranty, check the manufacturer's dead-pixel policy first.
What should I look for on the gray and gradient screens?
Uniformity problems: clouding and backlight bleed show up on dark grays, dirty-screen effect (faint bands and smudges) on light grays, and color banding — visible stripes instead of a smooth ramp — on the gradients. Perfect uniformity is rare; you are checking whether the flaws are bad enough to bother you.
Does this test work on phones, tablets, and TVs?
Yes — it runs in any modern browser. On iPhones, where true fullscreen is not available, the pattern fills the page instead: rotate to landscape and use the on-screen Exit button. For a TV, open this page in the TV's browser or mirror your laptop and step through the same patterns.