New Tricks in Fiddler

The new Fiddler Beta has a few useful tricks. First, you can copy a DataURI to your clipboard (from Fiddler itself, or anywhere else):


and use the new Edit > Paste Files as Sessions command:


… to instruct Fiddler to parse the DataURI and create a new Session for it. You can then use Fiddler’s inspectors to examine the resulting object:


Next, the WebView Inspector has been enhanced to render previews of WOFF font, MP3 audio, and H264 video responses, if you have IE9+ installed:




Lastly, Fiddler’s AutoResponder now permits you to use Regular Expression Group Replacements to map one URL to another. For instance, this rule:


…will convert to This capability makes it even easier to replace content using Fiddler’s AutoResponder.


This new build of Fiddler has a ton of other fixes and performance improvements. I hope you enjoy it!



Comments (9)
  1. JoeW says:

    Eric, love the new feature allowing regex to do URL replace.  I'm gonna use that a LOT.

  2. FremyCompany says:

    RegExp is so useful! I had the opportunity to use them so often I keep asking myself how I did without them… Many thanks.

  3. Andy Smith says:

    Fiddler seem to offer me all i could ever ask for except being able to switch the upstream proxy, gateay server on the fly and i've played with server pipes to try and switch servers but nothing seems to work.

    Swapping uptream proxy servers would allow developers to use elite but often slow proxy server for add-server requests and faster, more common transparant proxy servers for other request.

    For the life of me i still can not get my head around RegExp or Lander functions and would be lost without my own string extension methods

  4. Dan says:


    Could someone just explain the syntax shown in the example? Do the brackets indicate which bit should be inserted into $1 in the respond-with line? (maybe a couple more examples would be a great help if someone has time..?)


  5. EricLaw [MSFT] says:

    Dan– The parenthesis create what's called a "capture group", and .* means (any number of any characters). The $1 means "stick whatever was in the first capture group here." So the example in the screenshot grabs the tail of the first URL and puts it on the end of the second.

  6. Oleg says:

    I need to use Autoresponder for web service calls. I do not see how to create 2 different rules for 2 requests because Host+URL are teh same but only in the body I see the different method calls. Thanks.

  7. @Oleg: You're looking for URLWithBody, added in later versions.

    URLWithBody:Upload.php regex:^.*BodyText.*$

  8. Vadim says:

    Eric, I have problem with WevView to display the regular HTML responses. I have the XML responses displayed, but not the HTML. I am using the ver. and Firefox 17.

    I would appreciate your help.  thanks.

     EricLaw:  Please post questions to the Fiddler Discussion forum (see the Help menu) as I am no longer at Microsoft.

  9. Adam says:

    Awesome!! Just put the regex replacement to use 🙂

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