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.
- 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.
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.