Apple's latest MacOS software update may have brightened the display of your 2018 MacBook Air. Those who ultimately install the update will be pleasantly surprised that their notebook's retina display is suddenly brighter by 100 nits than before, resulting in a new brightness of 400 nits overall.
The brightness change was confirmed by users on Reddit and MacRumors . Apple's latest macOS 10.14.4 update, released on March 25, "fixes the standard screen brightness" of the latest MacBook Air models. Apple has also revamped the technical specifications of the new MacBook Air to indicate that the laptop's retina display has a maximum brightness of 400 nits, which exceeds 300 nits, so other technical releases and reviewers prior to the MacOS update from late March to December Detecting Their Systems
Brightness was one of the main problems we had with Air's new retina display when we discussed it last fall. Hopefully the new macOS update will fix this problem visibly.