Super User is a question and answer site for computer enthusiasts and power users. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

Say I want to use a proxy auto-config file that is stored at C:\proxy.pac. To make Internet Explorer use this configuration I have to specify the pac-file in the LAN settings in the following way:


But Safari, that uses the same proxy settings, will ignore it in this case. To make Safari use the pac-file I have to reference it as


(3 slashes at the beginning) which, according to Wikipedia is the correct format. But this way Internet Explorer will ignore it. Opera and Chrome, that also use the same proxy settings, are fine with both ways but is there another option that will work with Safari and Internet Explorer at the same time?

share|improve this question

For IE and the windows platform, the correct location for a local pac file seems to be:


next to your hosts file.

share|improve this answer
please note there is no extension – j040p3d20 Feb 13 '11 at 12:48

What happens if you use the dot, as Wikipedia also discusses: file://./C:/proxy.pac? So long as it is not on a sharename, this "spelling" of the path might be acceptable to both IE and Safari.

Alternatively, run a local webserver and serve the .pac file, then provide the URL as http://localhost/path/to/proxy.pac. That should work around the differences in path URL formats by avoiding using a path URL entirely.

share|improve this answer

this feature is no longer supported in W8.1 since the file:// protocol never was supported by winHttp. So tools that use whinHTTP for proxy settings will not recognize it. If you want to enable the file protocol for later version than IE10 you can always use the following registry key: Key:   HKLM\SOFTWARE\Policies\Microsoft\Windows\CurrentVersion\Internet Settings\  Value: EnableLegacyAutoProxyFeatures  Type:  REG_DWORD  Data:  1

share|improve this answer

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .