Fiddler

Fiddler lets you inspect traffic, set a breakpoint, and 'fiddle' with any incoming or outgoing data. Fiddler includes a robust event-based scripting system that can be extended using any .NET Framework language.

Easily edit web sessions: simply set a breakpoint to pause processing of the session and then alter the request or response. You can compose your own HTTP requests with the Composer and then run them via Fiddler, or return mocked responses with the AutoResponder.

Fiddler allows you to see the “total page weight.” Also, it lets you see HTTP compression and caching at a glance. In fact, you can isolate performance bottlenecks with simple rules such as “Flag any uncompressed responses larger than 35kb.”

Fiddler decrypts HTTPS traffic and displays and modifies web application requests using "man-in-the-middle" decryption techniques. You can configure Fiddler to decrypt all traffic or only specific sessions that you need. Benefit from rich extensibility modeling, that ranges from simple FiddlerScript to very powerful extensions that can be developed using a .NET Framework language.

Fiddler ensures that proper headers, cookies, and cache directives are transferred between clients and the server. Progress Telerik no longer actively develops Fiddler Classic and keeps it in maintenance mode, recommending Fiddler Everywhere for commercial work.

Fiddler Classic for Windows is a web debugging proxy, free for non-commercial use, that logs all HTTP(S) traffic between the Internet and your computer.

Features:

• Free Tool for Non-Commercial Use
• HTTP/HTTPS Traffic Recording
• List of ready-made add-ons
• Performance Testing
• Security Testing
• Set Break-points
• Web Session Manipulation
• Web Debugging

Fiddler Classic is free for non-commercial use and can debug Internet traffic from virtually any application or device that supports a proxy.