Monday, January 16, 2006

Minor beta introduces autodetect support

A new beta version of Fiddler has been released.

In the past, you manually had to specify an upstream proxy server in order for Fiddler to use the upstream proxy.

In the new version, Web Proxy Autoproxy Detection (WPAD) is supported, which should make it slightly simpler to get started with Fiddler if your environment requires a proxy server.

Please let me know if you have any questions or problems.

Introduced support for upstream proxy autodetection
Introduced support for upstream proxy configuration scripts (http/https delivered scripts only)
"Require proxy authentication" rule now shows 407s in session list
Updated copyright to 2006


  • What exactly does this mean? Do I no longer have to manually input as my proxy?

    By Anonymous Dave, at 6:25 AM  

  • If you were using WinINET, you never had to manually input anything as your proxy.

    No, this means that if you have an environment where you require a proxy server, and IE is configured to Autodetect that proxy server, Fiddler will properly autodetect that proxy server and use it. In the past, if you wanted to use an upstream proxy, you had to manually specify ~that~ before starting Fiddler.

    By Blogger Ericlaw, at 12:29 PM  

  • Hey Eric!

    Just installed Fiddler and it added the upstream proxy (HTTP) for my environment, but stripped out my exceptions that are needed to hit other resources on the network. Do I just need to plug these back in, or am I missing something?

    By Anonymous Drew C., at 3:21 PM  

  • The current version of Fiddler does not support Proxy bypass lists. If you use the "Autodetect" option, the bypass function of the WPAD file is resepected.

    As a workaround, you can add the following inside the Rules | OnBeforeRequest handler:

    if ( == "
    oSession.bypassGateway = true;

    By Blogger Ericlaw, at 2:28 AM  

  • Out of curiosity (as in I had a hard time doing it in .net, and if there is an more robust way, I'd like to follow it)
    How did you support WPAD in .net? Do you mind sharing?


    By Anonymous Anonymous, at 9:55 PM  

  • .NETv2 has built-in support for WPAD (although I'm not sure it's exposed directly).

    For Fiddler, I PInvoke down to WinHTTP, which exposes interfaces for WPAD detection and processing.

    By Blogger Ericlaw, at 1:47 AM  

  • Thank you for the help.
    Now that you pointed it out to me it seems obvious that the functions in WINHTTP are what I should have used instead of wininet.
    Ignorance is it's own reward, and I guess I have some rewriting to do. Either that or hope for a quick upgrade by the customers to .net 2

    Thanks again, for fiddler and for the pointer


    By Anonymous Anonymous, at 12:13 AM  

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