Screen brightness

Hi there becky55,

Thanks for using Apple Support Communities. It sounds like you want to know why your brightness changes by itself. The iPhone has ambient light sensors that will adjust brightness levels based on the light conditions around you. Learn more here: Adjust the brightness and color temperature on your iPhone, iPad, or iPod touch.

We hope this helps!

Hi again becky55,

Does it matter which way you are holding your phone or what time of day it is? Are you using a case on your iPhone? If you remove the case, does the brightness still change intermittently? Does it seem to happen when using certain apps or functions? Or does it happen when your iPhone is left untouched for a moment?

We look forward to hearing back.

It is Auto- Brightness and you can turn it off in settings.