Why Do Phones Automatically Brighten or Dim?

Imagine your phone has a tiny eye that can see how bright or dark it is around you. When it sees sunlight, it tells the screen to get brighter so you can still read. When it gets dark, it tells the screen to dim so it doesn’t hurt your eyes, just like when you turn on a night light at home.

This tiny eye is called a light sensor. It measures how much light is around and tells the phone what brightness level feels best for your eyes.