The significance of end-to-end testing in software development lies in its ability to validate the complete functionality of an application from start to finish. This comprehensive testing approach evaluates the performance and reliability of integrated systems, ensuring all components work together as intended. End-to-end testing helps identify issues that may not be apparent in isolated tests, ultimately improving software quality and user experience. By catching defects early in the development cycle, organizations can reduce costs associated with fixing problems post-launch and enhance overall project success.