Debugging Silverlight in Firefox 3.6.4 or later

Firefox just released an update, 3.6.4, which runs plugins such as Silverlight and Flash in a separate process. Unfortunately, this breaks the ability of Visual Studio to debug Silverlight applications.

You can restore debugging functionality by not running plugins in a separate process. Do this by:

  1. In Firefox, in the navigation toolbar address field, go to about:config
  2. Accept the "This might void your warranty!" warning
  3. Find the preference option named: dom.ipc.plugins.enabled.npctrl.dll
  4. Double-click it to set its value to false
  5. Shut down all instances of Firefox and Visual Studio