Fiddler Tutorial/Notes

    I after using Fiddler for a few years now, I wanted to jot some notes down for myself so I don't forget. I really like using fiddler and most of the time I prefer using it over the developer tools inside chrome just because I can use it across different browsers at the same time. This Saves me a lot hassle in opening the developer tool everytime but you might ask what is fiddler? "Its a web Proxy", where you can debug traffic calls, test the network performance and tons more stuff.  Fiddler is a .net application and will not run on other platforms however you can point clients to a host machine that is able to run fiddler and debug from there.


  • Traffic Import- Seeing a client's web experience.
    • FiddlerCap - lightweight version of fiddler more for client users, to allow you to see specific http request and responses even if you not on that network.
    • Example problems that you can use this for: DNS corruption
    • Poison DNS or other known as DNS spoofing
    • Does not support importing binaries 
  • Traffic Analysis 
    • Filtering 
      • To filter down to a process/browser: In the toolbar (if nothing set) "Any Process" crosshair icon.
      • To filter down to a process/browser: In the toolbar (if nothing set) "Any Process" crosshair icon.
      • Could also what you can do is in Rules option under User-agent for all browsers of a specific type.
      • To hide image request: Under Rules -> "Hide Image Request"
      • To filter down even more: The left tool boxes - under Filters
      • Find: use toolbar icon or cntrl-f.
  • Exporting - a collection of requests
    • copy sessions to the clipboard
    • store as a plaintext file
    • extract binary response bodies
    • archive to a database
    • export a visual studio .WebTest file
    • You can even write your own export (to even to a database!)
    • fiddler's native "Session Archive Zip file format"
  • "Viewers" Mode - allows examining multiple captures side-by-side
  • Buffering Mode -  the default mode, will wait until everything is collected before returning.
  • Streaming Mode - for performance testing  and speed profiles.
  • Request Builder - Edit previous requests and post them. 
  • AutoResponder - useful for changing things on the fly with Requests
    • If a site is down you can use a backup of the site locally.
  • Request Modification - Changes what is returned from requests
  • neXpert - much like Google's Page Insight or any other site audit. 
  • FiddlerCore, the .NET class library that lets you build Fiddler-like functionality into test frameworks and other tools
Side Notes
  • WinHttp - "designed to be used primarily in server-based scenarios by server applications that communicate with HTTP servers."
  • WinInet - "application programming interface (API)".
  • WinDiff -  "graphical file-comparison program 
  • ExecAction - "Scripting object that represents an action that executes a command-line operation."
    A lot of the information I got was on demoed at Microsoft Build and posted on Channel9:Advanced Web Debugging with Fiddler. After seeing the video I discovered I could be using fiddler to do so much more and this got me really excited to do more with fiddler. So I thought it was important to dig a little bit deeper on everything in the video. Also take a look at the Fiddler Commands for more options which I found to be interesting.

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