Capturing Localhost Traffic

Environment

Product
Product Version 1.0.0 and above

Description

Traffic sent to http://localhost or http://127.0.0.1 is not captured when using some browsers like Google Chrome or Firefox even though the Capturing mode of Fiddler Everywhere is turned on. How can I handle this issue?

Solution

Utilize either of the following approaches:

Both solutions require you to enable the Capturing mode.

Using the Machine Name

Use the machine name as an alias for localhost or the 127.0.0.1 loopback addresses. For example, if the machine name is myrootuserid, replace http://localhost:8081/mytestpage.aspx with http://myrootuserid:8081/mytestpage.aspx in the Shell.

Using Aliases

Depending on the specific scenario, you can replace localhost or 127.0.0.1 with one of the following special Fiddler aliases:

  • ipv4.fiddler for connections using Internet Protocol version 4.
  • ipv6.fiddler for connections using Internet Protocol version 6.
  • localhost.fiddler to hit localhost in the Host header (applicable for IIS Express).

For example, traffic sent to the following URL may not be captured:

http://localhost:8081/mytestpage.aspx

To capture that traffic with Fiddler Everywhere, use any of the following approaches:

  • Replace localhost with the ipv4.fiddler alias to hit localhost on an IPv4 adapter:

    http://ipv4.fiddler:8081/mytestpage.aspx
    
  • Replace localhost with the ipv6.fiddler alias to hit localhost on an IPv6 adapter:

    http://ipv6.fiddler:8081/mytestpage.aspx
    
  • Replace localhost with the localhost.fiddler alias to hit localhost in the Host header:

    http://ipv4.fiddler:8081/mytestpage.aspx
    

Filtering Localhost Traffic

While using one of the above solutions to capture localhost requests, the traffic will be captured in the Live Traffic list, and the loopback address will be displayed as a host name, usually 127.0.0.1. To filter by the Host column so that only localhost traffic is displayed, enter the loopback address, and not the aliases used in the browsers, as a host value.

Example Localhost filtering

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