Dart size vs external (native) size

Some parts of an object (for example, graphics)
might be stored outside of Dart heap,
in native device memory.

You can observe an object’s Dart heap, external,
and total memory allocation breakdown on the Profile tab:

Memory leaks happen in Dart?

Garbage collector cannot prevent all types of memory leaks, and developers
still need to watch objects to have leak-free lifecycle.

Why garbage collector cannot prevent all leaks?

While the garbage collector takes care of all
unreachable objects, it’s the responsibility
of the application to ensure that unneeded objects
are no longer reachable (referenced from the root).