If the slight changes to brightness while you are Web browsing or viewing any other dynamic content on the screen bother you, then you should look in your graphics driver settings for a feature that is described as 'power saving' and disable it. Windows 10 dimming screen when idle As stated in the title, my windows 10 installation recently updated and will now slowly dim my main screen after being idle for about 5 seconds, its extremely annoying because it will dim even while reading. We have found this behaviour to be tied to power management settings in graphics drivers, which, when disabled, allow the screen to maintain a constant brightness level. The subtle changes that occur when going from a dark background on the screen to a light coloured background have nothing to do with the 'Adaptive brightness' setting, but instead are a result of graphics driver settings. In that scenario, the brightness changes based on the room lighting.
That setting works using the ambient display sensor on a laptop. This behaviour is a dynamic brightness change that is unrelated to the 'Adaptive brightness' setting in Windows. These changes happen automatically after a couple of seconds, and they can also sometimes manifest as noticeable flickering. On a dark background, the screen will dim automatically, while on a bright background it will brighten. On some laptops, you may have noticed a change in brightness as you go from a screen with a dark background to a screen with a bright background.