Redux's core doesn't store any events or prior state by default. It just does: currentState = rootReducer(currentState, action); Time travel debugging is

Redux's core doesn't store any events or prior state by default. It just does: currentState = rootReducer(currentState, action); Time travel debugging is implemented as a store enhancer, which does indeed save the action history and replay it to generate the correct state as you jump between specific points in the history log. There's also many addons and additional use cases that can make use of recording actions as they occur, such as logging a user's session for later playback / debugging as part of a crash report, or implementing undo/redo functionality.