Fiddler
Fiddler is a free web debugging proxy tool that captures, inspects, and manipulates HTTP/HTTPS traffic between a computer and the internet. It allows developers to monitor network requests, analyze performance, debug web applications, and test APIs by intercepting and logging all traffic. Originally developed by Telerik, it is widely used for web development, security testing, and troubleshooting network issues.
Developers should use Fiddler when debugging web applications, testing APIs, or analyzing network performance, as it provides detailed insights into request/response headers, payloads, and timing. It is particularly useful for identifying bottlenecks, simulating different network conditions, and testing security vulnerabilities by modifying traffic in real-time. Common use cases include debugging AJAX calls, inspecting mobile app traffic, and automating testing scenarios.