How to configure Fiddler to listen to localhost

Question

I want to monitor HTTP traffic between a process on my local machine and another  server  process  also running on my local machine     How can I configure Fiddler to listen to traffic to and from localhost

User · Answer

Specific to Firefox  which does not go through Internet Options like IE  Chrome  and Edge do  you can use about config to modify preferences  find the preference network proxy no proxies on and remove localhost from it   This was the default setting for Firefox Developer Edition 66 0b2 and worked with Fiddler 5 0 20182 28034    Other listed solutions do work  this solution allows you to not change the host you are navigating to

User · Answer

Replace localhost by lvh me in your URL  For example if you had http   localhost 24448 HomePage aspx  Change it to http   lvh me 24448 HomePage aspx

User · Answer

By simply adding fiddler to the url  http   localhost fiddler 8081    Traffic is routed through fiddler and therefore being displayed on fiddler

User · Answer

tools    fiddler options    connections there is a textarea with stuff to jump  delete LH from there

User · Answer

try putting your machine name IP address instead of  localhost  into URL  Works for me

User · Answer

You cannot  Instead if you machine is named  myMachine   point your browser to http   mymachine instead of http   localhost

User · Answer

Replace localhost with 127 0 0 1 If it doesn t work change the run configuration to support your ip address

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I am running Fiddler v4 4 7 1  I needed to use localhost 8888 or machinename 8888 when using the Composer tab  Look at the Help About Fiddler menu option  where it says   Running on     Mine shows machinename 8888 there

User · Answer

The Light   You can configure the process acting as the client to use fiddler as a proxy    Fiddler sets itself up as a proxy conveniently on 127 0 0 1 8888  and by default overrides the system settings under Internet Options in the Control Panel  if you ve configured any  such that all traffic from the common protocols  http  https  and ftp  goes to 127 0 0 1 8888 before leaving your machine   Now these protocols are often from common processes such as browsers  and so are easily picked up by fiddler  However  in your case  the process initiating the requests is probably not a browser  but one for a programming language like php exe  or java exe  or whatever language you are using   If  say  you re using php  you can leverage curl  Ensure that the curl module is enabled  and then right before your code that invokes the request  include   curl setopt  ch  CURLOPT PROXY   127 0 0 1 8888     Hope this helps  You can also always lookup stuff like so from the fiddler documentation for a basis for you to build upon e g  http   docs telerik com fiddler Configure-Fiddler Tasks ConfigurePHPcURL

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And I just found out that on vista  localhost   will not work  In this case use  127 0 0 1    loopback address with a dot appended to it

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Go to proxy settings in Firefox and choose  Use system proxy  but be sure to check if there is no exception for localhost in  no proxy for  field

User · Answer

NET and Internet Explorer don t send requests for localhost through any proxies  so they don t come up on Fiddler    Many alternatives are available   Use your machine name instead of localhost  Using Firefox  with the fiddler add-on installed  to make the request  Use http   ipv4 fiddler instead of localhost   For more info http   www fiddler2 com Fiddler help hookup asp

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Rather than configure the application server and client to use another domain  you may want to configure the client application to use a proxy   Fiddler also creates a proxy you can use  logging all traffic   Rick Strahl blogged about using this in  NET Apps  I am always misplacing this blog post  so let me link it here  http   weblog west-wind com posts 2008 Mar 14 Debugging-Http-or-Web-Services-Calls-from-ASPNET-with-Fiddler   To be brief  the app config change is    lt system net gt     lt defaultProxy gt       lt proxy  proxyaddress  http   127 0 0 1 8888    gt           lt  defaultProxy gt   lt  system net gt

User · Answer

If you re using FireFox  Fiddler s add-on will automatically configure it to not ignore localhost when capturing traffic  If traffic from localhost is still  or suddenly  not appearing  try disabling and re-enabling traffic capture from Fiddler to goad the add-on into fixing the proxy configuration

User · Answer

Add a dot   after the localhost   For example if you had http   localhost 24448 HomePage aspx  Change it to http   localhost  24448 HomePage aspx  Internet Explorer is bypassing the proxy server for  localhost   With the dot  the  localhost  check in the domain name fails

User · Answer

This is easy  Just grab your computer s IP address with IPconfig at the command prompt  Then  hit the service using the IP address rather than localhost  You don t need to do anything to Fiddler to make this work  it will just work by itself

[localhost] How to configure Fiddler to listen to localhost?

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