Dead pixel test
Full-screen solid colours to hunt dead or stuck pixels: perfect for checking a new (or used) screen within the return window.
The test fills the screen with a sequence of solid colours (white, black, red, green, blue, grey) and two gradients: inspect the screen closely on each colour looking for dots stuck black or on a fixed colour.
Dead or stuck?
A dead pixel stays BLACK on every colour (its subpixels get no power). A stuck pixel stays lit on one fixed colour — red, green or blue — and shows best on black. Stuck pixels sometimes recover on their own or after a few hours of rapid colour cycling.
How to run the test
Go through every colour slowly: white reveals dead pixels, black reveals stuck ones, red/green/blue isolate the faulty subpixel. The gradients expose banding (colour bands instead of smooth blends). Look from 20-30 cm with a clean screen.
What warranties say
Many manufacturers tolerate a few defective pixels before granting replacement (ISO 9241-307 classifies panels by allowed defects). If you just bought the screen online from a business seller, in the EU you have 14 days from delivery to return it (private sales excluded): test it right away.