Windows 10 does not read a PAC file [RESOLVED]

If you are using Microsoft Windows 10, you may have an issue where it will not read the proxy PAC file that is hosted via FTP:// or FILE://

This issue occurs because Internet Explorer and Edge on Windows 10-based computers use the WinHttp proxy service to retrieve proxy server information. The WinHttp Proxy service does not support using the ftp:// or file:// protocol for a PAC file.

Example

  • You configured Microsoft Internet Explorer 11 or Microsoft Edge on Windows 10 to use the Use Automatic Configuration script option.
  • You are testing or deploying a proxy auto-configuration (PAC) file. You are storing the file in a local location, such as C:\temp\proxy.pac.
  • You specified the file location in the Use Automatic Configuration script option in Internet Settings by using the file protocol.
  • You created the following registry subkey: 
     HKLM\SOFTWARE\Policies\Microsoft\Windows\CurrentVersion\Internet Settings\Value: EnableLegacyAutoProxyFeaturesType:  REG_DWORDData:  1

In this scenario, the PAC file is not read by Internet Explorer.

Resolution

To resolve this issue, host the PAC file on a web server, then refer to it by using the http protocol.   Do not host the file on the local machine, this will not work.

Duncan Newell

Duncan is a technology professional with over 20 years experience of working in various IT roles. He has a interest in cyber security, and has a wide range of other skills in radio, electronics and telecommunications.

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