Key Features

Customizable Free Tool

  • Extending Fiddler with FiddlerScript and .NET code

    Web developers can easily extend Fiddler using the .NET Framework. There are two way to go about it: create either Custom Rules or Inspectors.

    Read more in the Documentation

  • Fiddler extensions and add-ons

    Fiddler’s rich extensibility model enables developers to add powerful new features to Fiddler via easily installed add-ons. Among the most popular 3rd party extensions are the ones that enhance Fiddler’s ability to test the performance and security characteristics of web applications.

    See full list of Fiddler add-ons

  • Adding inspectors

    An alternative way to extending and customizing Fiddler according to your needs is by adding Inspectors which can be written in any .NET language. Inspectors can be read-only or read-write. If an Inspector is read-write, you can use it to modify the HTTP request or response before the server or the client receives it. The changes you make while the paused at a breakpoint are committed automatically by the Inspector.

    A quick list of commonly used request/response Inspector types includes:

    Request Inspectors

    [RW] Headers—Shows request headers and status.

    [RW] TextView—shows the request body in a text box.

    [RO] XML—shows the request body as an XML DOM in a tree view.


    Response Inspectors

    [RW] Transformer—Removes GZIP, DEFLATE, and CHUNKED encodings for easier debugging.

    [RW] Headers—Shows response headers and status.

    [RO] ImageView—shows the response body as an Image. Supports all .NET image formats.

    [RO] XML—shows the response body as an XML DOM in a tree view.

  • Creating rules

    Fiddler supports a rich extensibility model which ranges from simple FiddlerScript to powerful Extensions which can be developed using any .NET language.

    Rules are the primary way to extend Fiddler – in essence, it’s a JavaScript file that contains commands to extend Fiddler’s UI, or modify the session request and response. You can extend and customize the rules menu – for example the sub-menu items like user agents get populated from your JavaScript file.

    There are various rules that you can start using out of the box:

    • Hide image requests – control if you’d like to see returned images in the session list
    • Hide connects – decide if you’d like to see the original, raw connection to the server
    • Automatic breakpoints – use if you’d like to have Fiddler automatically breakpoint before/after each request and response.
    • Remove all encodings – removes all HTTPs request/response encodings
    • Hide 304s – gives you the option to hide all HTTP responses that have not been modified
    • Choose among user-agents or set a custom value

    Alternatively, you can create your own custom rules by using FiddlerScript.


Next Steps?

Download Now

Get Telerik Fiddler web debugger. It's free.

Explore More Telerik Tools

Recognized by the industry.