Setup a native proxy switcher on Firefox

README.md

• Download script.pac to /home/user/script.pac
• Go to FF network settings and select 'Automatic proxy configuration URL'
• Enter file:///home/user/script.pac
• Enjoy

Note: If you're using SOCKS v5 you might want to also select 'Proxy DNS when using SOCKS v5'

Tested on 116.0.2 (64 bit) Arch Linux

script.pac

function FindProxyForURL(url, host) {
    if (
      (dnsDomainIs(host, ".my-domain"))
      && !(dnsDomainIs(host, ".other-domain"))
    ) {
      return "SOCKS localhost:2000;"; // SOCKS V5
    } else {
      return "DIRECT";
    }
  }
// See https://developer.mozilla.org/en-US/docs/Web/HTTP/Proxy_servers_and_tunneling/Proxy_Auto-Configuration_PAC_file for more information on the syntax.

Good to know: If you enable the automatic detection of settings, Web Proxy Auto-Discovery Protocol will fetch the PAC file it was set up with for all your devices, with the needing to enter the URL every time.

For chromium based browsers, see: https://www.chromium.org/developers/design-documents/network-settings and https://chromium.googlesource.com/chromium/src.git/+/HEAD/docs/proxy_auto_config.md