Match Fiddler AutoResponder on body content

It’s possible to get Fiddler to manipulate your responses before they are returned to your application when Fiddler is acting as a proxy to your application.

Interestingly I couldn’t get the Chrome Advanced REST Client to go through Fiddler, but Chrome PostMan worked without any issues.

After you’ve setup your app to use your local Fiddler port, open up the AutoResponse tab.

  • Tick the enable rules checkbox to use the AutoResponse feature
  • Tick the Unmatched Requests Passthrough to enable other responses that don’t match a rule to continue to their destination
  • Items at the top of the list will get matched first
  • The first item that is matched will return the configured response
  • You can drag items from the traffic history into the responses dropdown, and edit the response. Really cool!

Here are some useful matches:

  • URLWithBody:REGEX:example.com REGEX:example
    This lets you match the url and body with regular expressions
  • Header:MyHeader=exactmatch
    Match a particular header

Struggling matching? It might be an encoding thing or you might want to see more rules (tip: click the dropdowns in the Rules Editor to see some built in examples).