Due to popular request, I wanted to add a quick post with instructions on using Fiddler as a web proxy allowing you to capture all your browser traffic from Firefox on OSX (or any other platform for that matter). I posted a while back on how to setup a Windows SQL Server virtual machine using VirtualBox as the DB server for our Rails project. Now I’m going to take that a step further and put the VM to more good use. Anyone who has tried to run Wireshark to filter HTTP traffic will appreciate this…

 

Fiddler Setup

Unfortunately, Fiddler is a Windows-only installation and won’t run natively on OSX... So after installing it on your Windows VM, configure the following to allow remote connections. This will expose a service on port 8888 on the VM allowing you to setup a Firefox proxy on your host OS.

 

Fiddler

 

Firefox Setup on OSX

I like using Firefox over Chrome on OSX for capturing HTTP traffic because Firefox allows you to configure a proxy for browser traffic only. The Chrome configuration forces you to proxy your system’s network connection. It’s not a big deal, but if you proxy traffic from your network connection rather than just your browser, you might catch a lot of unwanted traffic from other connected applications. I guess it just depends where you want to do your filtering…

 

It’s a simple configuration in Firefox. Just go to the Advanced tab of your Firefox preferences and click the Settings button under the Connection section. Edit the Manual proxy configuration to point at your Fiddler service running on the Windows VM. A quick note here if you didn’t read my VirtualBox setup post. I have two network connections configured on the VM – a NAT network adapter for regular Internet traffic and a Host-Only adapter for database traffic, etc. The IP configured below in the Manual proxy configuration is the Host-Only adapter’s IP address.

 

Firefox1   Firefox2

 

And that’s it! Happy Fiddling!

Just a quick reminder to un-proxy your Firefox traffic when you’re done because the active Fiddler service is required. Your Internet connection will be disabled as soon as you shut down Fiddler if you don’t.