Persistently Filtering Out Application Traffic in Fiddler - fiddler

Question

Whenever I start Fiddler, I see traffic from all of the applications on my system but it's very rarely the case that I want this. Usually what I want is to only see requests made by applications I am debugging. In order to achieve this, I leave Fiddler running all the time and whenever I want to see what happened with a request I can just open it up and see.
I can filter requests by right-clicking on an entry -> Filter -> Hide '<application name>'. Although this works fine, it is cleared when Fiddler is restarted.
How can I persist filters that filter out traffic from a certain application?
I tried using the Filters tab but this is very limited and one of the missing features is what I detailed above.

Answer 1

This can be achieved by creating custom rules. In order to do this, in Fiddler, go to Rules -> Customize Rules. You can choose Yes to install the FiddlerScript Editor plugin if you want but this is not necessary. Just click No when asked and a file named CustomRules.js will be opened using Notepad.
This file allows you to program all sorts of rules into Fiddler, from adding headers to outgoing requests to monitoring the time taken for a response to be received. Further details on it can be found here.
In order to filter out a certain application, scroll down to the OnBeforeRequest method and paste the following code in:
if (oSession["X-PROCESSINFO"] && (
oSession["X-PROCESSINFO"].StartsWith("firefox") ||
oSession["X-PROCESSINFO"].StartsWith("outlook") ||
false))
{
oSession["ui-hide"] = "FiddlerScript> Hiding unimportant process";
}
This piece of code tells Fiddler to hide all requests coming from Mozilla Firefox or Microsoft Outlook. If you want to add / update / delete any application here, all you need to do is copy / update / delete lines that contain the StartsWith method.
The first condition will filter out all the requests that do not come from an application. This is the case for requests made from Fiddler's Composer tab.