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

Answer 1

By simply adding fiddler to the url

http://localhost.fiddler:8081/

Traffic is routed through fiddler and therefore being displayed on fiddler.

Answer 2

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.

Answer 3

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.

Answer 4

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.)

Answer 5

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

Answer 6

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.