Unlike most browsers, Safari doesn't have a setting to use WPAD (web proxy auto-discovery) in OS X. However, there is a way to ask Safari to automatically detect the network's proxy settings, but only if your network administrator has configured WPAD on your network.
This auto-detect feature works through DNS. The browser looks for a host named "wpad" and if it exists, loads its settings by accessing a file named "wpad.dat" via HTTP. To use DNS-based WPAD with Safari on OS X, follow these steps:
- In Safari, choose Safari » Preferences
- Click on the Advanced icon
- Click on the Proxies » Change Settings button
- In the Configure Proxies dropdown menu, select Using A PAC File
- In the PAC File URL field, enter http://wpad/wpad.dat
- Click on OK
- Click on Apply
Again, this is only helpful if your network administrator has set up a proxy to be auto-configured. If you're on a network that doesn't have such a setup, Safari will still work but
much, much slower. To find out if your network supports proxy auto-detection, visit
http://wpad/wpad.dat in your web browser. If your network supports WPAD, then your browser will download the file "wpad.dat" (which you can just delete). If it's not supported, you'll get an error message.