How system proxy work in Windows 10 and 11

Question

Hi Experts,

Just some doubts about the LAN settings in Internet Options, shown as below:

The options :

1. How does  Automatically Detect Settings work?  

Who (browsers? Or Windows OS, or other applications) will use this option?

What it/they will detect for determination?

What rules they will follow to use proxy or not?

2. Use automatic configuration script:  it will be a PAC file.

(1) Is it only be used by browsers? (IE/Edge/Chrome/Firefox), I know there is a switch on Firefox to enable/disable system proxy?

(2) Is it used for https/http (TCP 443/80) traffic only? Will Other protocol's traffic use it(like SMTP/FTP/ICMP)? or it depends on the client/application? I know some application has the option to select use Proxy or not, but some of them don't have this option.

(3) Will it be used by other applications? like CMD Ping 8.8.8.8, or PowershellS : test-netconnection www.google.com -port 53

      Or other SFTP client to connect to the server by SFTP protocol, 

      Or use a browser to access FTP server

(4) Who will decide to use it or not?  I mean will Windows force the browsers/applications/commands to use it, or they can decide by themselves?

3. Proxy Server **** Under this option, we can set Proxy server manually, will it conflict or duplicate with above PAC file? which one has higher priority?

The above did confused me a lot and if there is detailed document for the above options/menus that will be great.

Thanks very much

***moved from Windows / Windows 11 / Internet and connectivity***

Answer 1

Hello,

When you’re connected to the internet and using a proxy server while browsing the web, that traffic goes through the proxy server instead of coming directly from your Windows 11 PC. A proxy server can be used when you’re connected using Wi-Fi or Ethernet. In some cases, your company or organization might require a proxy server.

To use a proxy server, you’ll need one or more of the following things, depending on how you’re setting it up:

• Automatically. Windows detects the proxy server settings automatically, so you don’t have to enter any information.
• Set up script. You’ll need to know the location of the proxy setup script for your organization (if proxy settings aren’t detected automatically).
• Manually. You’ll need to know the proxy server name or IP address and port (optional). If you don’t have this information, you might need to contact your IT department.

Use a proxy server in Windows - Microsoft Support

Best Regards

Zunhui