What is the foundation for Flutter?

kReleaseMode top-level constant Null safety A constant that is true if the application was compiled in release mode. … Since this is a const value, it can be used to indicate to the compiler that a particular block of code will not be executed in release mode, and hence can be removed.

Core Flutter framework primitives. The features defined in this library are the lowest-level utility classes and functions used by all the other layers of the Flutter framework .

The Foundation library , written in Dart, provides basic classes and functions that are used to construct applications using Flutter, such as APIs to communicate with the engine.