Some Windows 11 PCs can automatically adjust the screen brightness and contrast based on content that’s displayed on your built-in screen. For example, if you’re watching a video that has a dark scene, followed by a brighter scene (for example, one that shows a bright sunny day), the brightness and contrast may change. This is normal.
Content adaptive brightness control provides ideal brightness and contrast levels, while saving power and providing longer battery life at the same time. If these sudden brightness changes are distracting, or if you work in photo and video apps where color accuracy is important to you, you can turn this off any time. When you turn it off, it can result in shorter battery life.
To turn off Content adaptive brightness control
Select the Start button, then enter settings. Select Settings > System > Display.
In Display settings, select Brightness, then clear the Help improve battery by optimizing the content shown and brightness check box. You can select the check box to turn this back on any time.
Some Windows PCs can also adjust the screen brightness automatically based on the light around you. For more info, see Change screen brightness in Windows.