This article was created in response to a support issue logged with K2. The content may include typographical errors and may be revised at any time without notice This article is not considered official documentation for K2 software and is provided “as is” with no warranties.


This should be done for debugging purposes, i.e. when you want an easy way to redirect all K2 HostServer web traffic to go through Fiddler.

Running Fiddler like this should only be done for debugging purposes and never on Production Systems.


There is a wide range of issues that can be debugged using these instructions, from SmartAction Notifications, K2 for SharePoint Applications and even SmartForms.

Troubleshooting Steps

Please follow these instructions:

1. Download the latest copy of Fiddler here:

2. Stop the K2 Blackpearl Server

3. Open "\K2 blackpearl\Host Server\Bin\K2HostServer.exe.Config"

4. Add the following to the <> section. 

<defaultProxy enabled="true" useDefaultCredentials = "true">

    <proxy autoDetect="false" bypassonlocal="false" proxyaddress="" usesystemdefault="false" />


These values are from the Denallix core’s Fiddler config so please adjust accordingly for your environment!

5. Restart the K2 Blackpearl Server.

Now your host server will route all web traffic through Fiddler. You can easily disable this by changing the enabled flag to false as indicated below and restarting host server.

<defaultProxy enabled="false" useDefaultCredentials = "true">

    <proxy autoDetect="false" bypassonlocal="false" proxyaddress="" usesystemdefault="false" />


Once you enable host server traffic through fiddler you’ll start to see entries like the following:
(The following example is when K2 is getting OAuth Tokens):