What is YAGNI?

YAGNI stands for "You Aren't Gonna Need It." It is a principle of extreme programming (XP) that states a programmer should not add functionality until deemed necessary. The rationale is that writing code that is not needed is a waste of time and effort, increases complexity, and can potentially introduce bugs or be difficult to maintain. It encourages developers to focus on implementing what is immediately required by the project and avoid premature optimization or adding features based on speculation about future needs.