Right-click the taskbar
Select Taskbar settings
Turn on Automatically hide the taskbar
On Windows 10, open Settings
Go to Personalization
Select Taskbar
Enable Automatically hide the taskbar in desktop mode
Enable Automatically hide the taskbar in tablet mode if needed
On Windows 11, open Settings
Go to Personalization
Select Taskbar
Open Taskbar behaviors
Check Automatically hide the taskbar
Close Settings