I am trying to debug an issue with a website that is extremely intermittent. To do this I have set up fiddlercore as a service on my machine so that it automatically runs at start-up and captures all traffic until the issue presents itself again.
Unfortunately having fiddlercore proxy all of my internet traffic is slowing my web browsing down and preventing certain sites from displaying correctly.
I tried to get around this by telling fiddler not to be the system proxy and having a remotely hosted PAC file regexp match the site I am interested in and point it to PROXY 127.0.0.1:8080 but this seemed to confuse fiddler and I got stuck in a redirect loop.
Is there any other way I can have fiddler as the proxy, but only for the sites i specify?
If your FiddlerCore application is written correctly and your certificates are configured correctly, it won't cause any problem with any websites. You haven't shared any code, so it's hard to help you with that.
You also haven't shared your "remotely hosted PAC file" script, so it's hard to tell if there's something wrong there, but, in principle, using a PAC file to selectively send traffic to FiddlerCore will work just fine, so long as you don't configure FiddlerCore to adopt the upstream proxy settings.
For instance, if you fail to unset the FiddlerCoreStartupFlags.ChainToUpstreamGateway flag, you'll encounter this problem.