Normally, a Debug banner appears in the top right corner of the screen. while we’re building the flutter app. Whenever we create a flutter app, the debug banner comes by default.
The debugShowCheckedModeBanner property in the MaterialApp constructor is responsible for displaying or hiding the debug banner.
How to remove Debug Banner:
This Debug banner indicates that the app is in debug mode. By making the debugShowCheckedModeBanner property to false, we can disable the banner.
MaterialApp( debugShowCheckedModeBanner: false, //.. )
When the application is in debug mode, this debug banner is supposed to deter people from complaining about how slow it is.
Flutter enables a vast amount of expensive diagnostics in debug mode to aid in development, Hence performance in debug mode is not representative of performance in release mode.