When to use .add() and when to use emit() in Flutter Bloc?

Use emit when you want a new state for your bloc.
Use add when you want your bloc to handle a new event.

See the Timer tutorial as an example.

You should always use emit, flutter bloc was upgrade to extends Cubit class and Cubit uses emit. Add was old usage.

I would also suggest you to look up this official plugin before getting started to implement bloc on your project.

• https://pub.dev/packages/flutter_bloc

For more examples see this - https://github.com/felangel/bloc/tree/master/examples