The difference between Agile and Waterfall is a common question when it comes to choosing software development methodologies. Some of the key differences are: Agile is iterative and invites testers to participate at different stages. Waterfall follows a linear approach and testing happens at the end. The Agile definition stage happens at the beginning of each sprint while Waterfall’s definition is extensive and blocks all the other stages after that. Agile admits and fosters changes at any stage. Waterfall discourages changes after the definition stage.