A dead pixel is a picture element in which all three RGB (red, green, blue) sub-pixels are permanently turned off, which creates a black spot in the display.
A dead pixel is like a popcorn hull in your gums: It's not going to kill you, but once you've noticed it, you'll probably never manage to un-notice it.
Your device's display is made up of millions of pixels. Each pixel is a group of the colors red, green and blue subpixels that combine to make any color needed and they create the images you see on your computer screen.
Dead pixels occur when a single pixel in a display stops lighting up, causing a persistent black dot on the screen. It's fairly difficult to fix a dead pixel, and often requires replacing the screen.
Malfunctioning transistors and manufacturing flaws can result in dead pixels. Dead pixels are often confused with stuck pixels, which have a different cause and effect. Each pixel in a display is made up of three sub-pixels: one red, one green and one blue. In a stuck pixel, one or more of the three remains turned on so that the pixel displays consistently as a particular color rather than refreshing along with other display content.
STUCK PIXEL VS DEAD PIXEL
A stuck pixel occurs when one or two of the color subpixels remain activated even when they're supposed to be off. For example, the blue subpixel might get stuck so the entire pixel will display a different color than what is intended.
A dead pixel occurs when an entire pixel or a group of subpixels remain dark even when they're supposed to be on. Since this implies that the pixel or group of subpixels are no longer powering on, they're harder to fix than stuck pixels. In most cases, dead pixels are lost forever.
Depending on their number and position on the screen, dead and/or stuck pixels can impact the user experience. Both dead pixels and stuck pixels have been reported to disappear (and sometimes reappear) over time. Although stuck pixels are thought to be easier to address than dead ones, a number of DIY fixes and software products offer help for both issues.
"Dead" and "stuck" aren't interchangeable names. Dead is dead. They're purely black or white spots, and are rarely resurrected. Stuck is just stubborn—these sometimes respond to remedies (which we'll get to in a moment). A stuck pixel can show up as any color of light, but is most often red, green, or blue.
How to Fix a Dead Pixel on Your Monitor, Smartphone, or Tablet
I. Use your warranty
If you are within your display's warranty period and you have detected stuck or dead pixels, it's recommended that you have the manufacturer replace it.
Most monitor manufacturers have a return policy for dead and stuck pixels and they'll usually replace a monitor if it has more than several pixels stuck in a single color or brightness setting. Additionally, since dead pixels are difficult to fix, replacing your monitor via the manufacturer's warranty is your best route.
II. REPLACE THE SCREEN
The most reliable way to fix a dead pixel is to replace the screen. Many manufacturers have warranties that cover dead pixels, so check your device's warranty to see if this situation applies to you.
Most display manufacturers require a minimum number of dead pixels before the screen can be replaced. For a display the size of a computer monitor, the minimum is typically four to eight dead pixels. Smaller displays have lower minimum requirements.
Unfortunately, a small number of dead pixels are expected, and one is rarely enough for replacement. At this time, only Dell and BenQ offer a screen replacement for just one dead pixel. You can examine the dead pixel policies of Acer, Asus, Apple, BenQ, Dell, LG, and Samsung, but the best source will always be your device's specific warranty documents.
III. WAIT FOR THE PIXEL TO DISAPPEAR
You can try waiting for the dead pixel to go away on its own. This has been known to happen, but no one can say when. You might have the dead pixel for the remainder of the device's life, or it might go away in a week. It's impossible to say.