iPad Pro 2018 ipad pro brightness randomly dimmed

[ipos]

the brightness will randomly dimmed if used continuously my ipad pro for a while i.e. 45 mins
after my ipad is unused for a while, brightness is back to full

 

[xxFoxtail]

The screen dims if it’s overheating.

 

[ipos]

Is this a built-in feature that has been the case for all idevices? My ip12 pro max also has this issue

 

[sparksd]

Is this a built-in feature that has been the case for all idevices? My ip12 pro max also has this issue

Yep, it's the device doing self-protection.