Why does my iPhone screen dim by itself?

Your iPhone screen usually dims by itself because of Auto-Brightness, heat protection, Low Power Mode, or display settings like Auto-Lock and Attention Aware Features.

Most common reasons:

• Auto-Brightness adjusts the screen to room light.
• Heat from gaming, charging, navigation, or sun can make iOS dim the display to protect the phone.
• Low Power Mode can reduce brightness-related behavior to save battery.
• Auto-Lock may dim the screen right before it turns off.
• True Tone / Night Shift can make the screen look dimmer.
• Attention Aware Features can change dimming behavior on Face ID iPhones.

Quick checks:

• Settings → Accessibility → Display & Text Size → Auto-Brightness
• Settings → Battery → Low Power Mode
• Settings → Display & Brightness → Auto-Lock, True Tone, Night Shift
• Settings → Face ID & Passcode → Attention Aware Features

Best quick fix: turn off Auto-Brightness temporarily, disable Low Power Mode, and let the iPhone cool down. If it still dims a lot, restart the phone and update iOS.