Apple has published a new support document for owners of the redesigned 2021 MacBook Pro and Apple Pro Display XDR, explaining the meaning behind the warning icons that appear with a “limited brightness” message in the Mac’s menu bar.
Apple notes that if the ambient temperature of a room is high and the user has been viewing bright content for an extended period of time, the Liquid Retina XDR display on the MacBook Pro and the Apple Pro Display XDR will automatically turn on “low power mode” and dim the display due to overheating concerns.
Apple suggests that users of the MacBook Pro who see the “limited brightness” message should consider quitting any apps that could be consuming significant system resources, lowering the ambient temperature of the room and putting their Mac to sleep for 5-10 minutes.
Owners of the Apple Pro Display XDR are advised to close or hide any windows with HDR content, use the Apple XDR Display or Pro Display XDR reference mode unless your current workflow requires a specific reference mode, and again lower the ambient temperature of the room.
The support document says if the issue continues and the ambient temperature of the room is less than 77° F, contact Apple Support.