At what phase of the SDLC methodology do we write use cases?

In the Software Development Life Cycle (SDLC), use cases are primarily written during the Analyze phase. This phase focuses on understanding the requirements of the system by gathering and analyzing the needs of stakeholders. Use cases serve as a tool to document the functional requirements of the system by describing how users will interact with it. Each use case outlines a specific scenario in which a user achieves a goal within the system, providing clarity and guiding the design and implementation phases that follow.

In contrast, the Plan phase is more about project management—identifying the scope, resources, and timeline for the project rather than detailing the functional interactions. As a result, use cases are not typically developed during the planning stage, as the emphasis lies on defining the overall strategy rather than the specifics of user interactions.