How does Singleton violate the single responsibility principle (SRP)?

Singleton violates the single responsibility principle (SRP) because it combines two different roles that should be split between different classes:

#The business-logic role

For example, the Logger class is responsible for writing logs, ConfigManager for storing settings, Cache for caching data. That is their core responsibility.

#The lifecycle-management role

Singleton forces those same classes to control their own creation, hold a reference to the single instance, and provide global access to it.

This design makes the class too "smart": it does not just solve a task, it also manages itself. This violates the SRP, under which a class should have only one reason to change.

When one part of the system must change because of the logic, and another because of the initialization approach, a change in one aspect affects the other. As a result, the code becomes less flexible, harder to test, and more tightly coupled to global state, which contradicts the idea of a clean, modular architecture.