Our applications start to grow, our technical skills evolve, technical debts need to be fixed… and at that moment you don't know where to start the refactoring? In this presentation you will learn the principles of refactoring, code smells and refactoring techniques: Extract Function, Extract Variable, Encapsulate Variable, Introduce Parameter Object, Split Phase, Extract Class, Remove Middle Man, Hide Delegate, Move Function, Remove Dead Code , Change Value to Reference, Decompose Conditional, Introduce Assertion, Replace Constructor With Factory Function, Pull up method, Extract Subclass and Collapse Hierarchy techniques based on Martin Fowler's book Refactoring