The taskbar can house pinned apps that you use frequently. If you have an app open, it’s icon will also be displayed on the taskbar to indicate that its running. Furthermore, if you hover your mouse cursor over the taskbar icon of an open/running app you will get a small preview window of the app. The taskbar is pretty great and some might find it’s more efficient than the Dock on macOS. The pinned app icons on the taskbar appear only on your main display. The secondary display doesn’t show the pinned apps. If you happen to change you primary screen a lot, and both your screens are different sizes, you could benefit from using AdaptiveTaskbar. It’s a free open source app that can change the taskbar icon size based on screen size.
Adaptive Taskbar icon size
Taskbar icons are bigger if you’re using a bigger screen. On smaller screens, the icons that are displayed are much smaller or so they should be. Unfortunately, Windows 10 only lets you choose between using either large or small icons.
If you often disconnect an external display which happens to be much bigger than your main/internal display, you may not want the large taskbar icons to be used. At the same time you may not want to manually change their size every single time you switch your primary screen or disconnect the external display. To fix that, you can install AdaptiveTaskbar and leave it running in the background. It will proactively change taskbar icon size based on screen size.
Screen size vs resolution
An important distinction to make when using this app is between screen size and screen resolution. Two screen that are different sizes can have the same resolution. A 21 inch screen can have the resolution 1920×1080 and a 15 inch display can have the same resolution.
The difference is that on the 15 inch display the pixels are packed much closer and things tend to look much smaller. You may use scaling to ‘fix’ this since Windows 10 allows you to set different scaling levels for different screens. The point is, just because your screens have the same resolution, it doesn’t mean that the items on your screen scale 1:1 between them. That only happens if both the screen size and the resolution are the same.
AdaptiveTaskbar is an app exclusively for multi-monitor set-ups. If you only use a single screen, this app isn’t for you. It reacts to whichever is your primary monitor so even if you do not disconnect a monitor, you can simply change which one you use as the primary one and the app will adjust the size of the taskbar icons.