Localhost Traffic Capturing

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 Fiddler Everywhere Capturing is turned on.

Solution

To solve this issue, use either of the following approaches:

Both solutions require that Fiddler Everywhere Capturing is enabled.

Using Machine Name

Use the machine name as an alias for localhost or 127.0.0.1 loopback addresses.

For example, let's assume the machine name is myrootuserid Instead of using localhost like this:

http://localhost:8081/mytestpage.aspx

Use the machine name as follows:

http://myrootuserid:8081/mytestpage.aspx

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 the traffic with Fiddler Everywhere:

  • 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
    

Filter Localhost Traffic

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

Example Localhost filtering

In this article