What is a dead pixel?
A dead pixel is a pixel whose transistor has failed permanently. It never produces light, so it appears as a tiny black dot on your screen regardless of what is being displayed.
Dead pixels are caused by manufacturing defects, physical pressure, or age. No software can fix a dead pixel because the hardware itself is broken.
What is a stuck pixel?
A stuck pixel has a transistor that is permanently on (or partially on) in one sub-pixel channel. It appears as a tiny dot of red, green, or blue that does not change with the image.
Unlike dead pixels, stuck pixels have a chance of being fixed. Rapid color cycling can sometimes wake up the stuck sub-pixel by exercising the transistor.
How to tell the difference
Can you fix them?
Dead pixel: No. The transistor is physically broken. If your monitor is under warranty and has enough dead pixels to meet the manufacturer replacement policy, contact them.
Stuck pixel: Sometimes. The Stuck Pixel Fixer flashes colors rapidly at the pixel location, which can exercise the transistor back to life. Success rates vary, but it is worth trying before returning the monitor.
When to worry
A single dead or stuck pixel on a 4K display (8.3 million pixels) is cosmetically minor. If you notice clusters of dead pixels or new ones appearing over time, it may indicate a deeper panel issue.