The main purpose of performance testing in software development is to evaluate how a system behaves under various conditions, ensuring it can handle expected workloads effectively. This testing measures factors such as response time, speed, scalability, and resource usage. By identifying potential bottlenecks and issues early in the development process, teams can optimize the application for better performance before deployment. Performance testing helps ensure user satisfaction by delivering a seamless and efficient experience, especially during peak usage periods. Ultimately, it plays a crucial role in maintaining overall system reliability and stability.