Display brightness always at full
Display brightness setting always set at full
iMac 27″, macOS 26.5
Question marked as
There are many ways to adjust brightness:
Change your Mac display’s brightness - Apple Support
If none of those are working, test in a new user account:
Add a user or group on Mac - Apple Support
See if the problem is present when you boot in safe mode, which disables 3rd party extensions and performs some system cleanup.
Start up your Mac in safe mode - Apple Support
It might help to download and run EtreCheck, written by a long-time forum member. The free version is fine. Post the full report using the Additional Text button. No personal information is revealed.