Clean your screen, then click Start the test. The screen fills with one color at a time: look closely for any dot that doesn't match.
Click, tap, or press → or Space for the next color, ← to go back, and Esc to finish.
Stuck pixel fixer
A stuck pixel (one that stays red, green or blue) can sometimes be revived by flashing colors over it for a while. It rarely helps a dead (always black) pixel.
⚠ Flashing lights. The fixer flashes rapidly changing colors. Don't use it if you or anyone watching is sensitive to flashing lights or has photosensitive epilepsy.
Drag the square over the stuck pixel and leave it for 10 to 30 minutes. Press Esc or click Stop to end.