Proxy Auto-Configuration URL

One of the easiest ways to change your IP address with a proxy server is by using a proxy auto-configuration URL in your web browser. A  proxy auto-configuration URL tells your browser when to use a proxy server, and what proxy server hostname and port to use.

How does a Proxy Auto-Configuration URL Work?

A proxy auto-configuration URL instructs your web browser to download a javascript  PAC file, normally called proxy.pac, which contains at least one javascript function called FindProxyForURL

Most of the time, this function simply tells your browser to always use a specific proxy server hostname and port for all requests. But the function can also restrict proxy usage based on the request. For example, a proxy server might only support HTTP requests, but not HTTPS requests. 

In that case, the function would examine the request, and if it's for a HTTPS URL, it would tell the browser to skip the proxy and go directly to the site. However, if the request is for a normal HTTP URL, then the proxy would be used. 

ProxyMesh supports both HTTP requests and HTTPS requests, and so the proxy.pac auto-configuration function will work as both a http proxy server and a HTTPS proxy server, but will ignore any non-HTTP requests.

How do I use it with an Authenticated Proxy Server?

Because proxy auto-configuration URLs do not support specifying proxy usernames and password (and for good reason, because it would be a security risk), you must use  IP address authentication

Once your IP is registered with the proxy server, then the proxy auto-config will handle the rest, by specifying the proxy server hostname and port for each request.

How do I set up Automatic Proxy Configuration?

First, you need a proxy auto-config URL to use. ProxyMesh provides all subscribers with this URL in the  account dashboard, which you can find after you signup for ProxyMesh.

Once you have a URL to auto-config the proxy, you must go into your browser's proxy or network settings and look for a setting such as  Automatic proxy configurationAutoconfiguration URLAutomatic proxy configuration URL, or PAC File URL, and then copy/paste the URL.

Once you save this URL in the settings, your browser will be using the automatic proxy configuration for all future requests.

How do I create a PAC file if I’ll be using more than one proxy?

On the dashboard, the .pac files shown in the Auto-Config URL column are for only 1 proxy each, whereas Make Custom Pac File can combine multiple proxies. Use the Make Custom PAC File link on your dashboard to create a .pac file that will randomly choose from multiple proxies for each request.

Before following this link, make sure you've selected all of the proxy checkboxes that you want access to from the proxy list on the Dashboard. You can modify your access here: https://proxymesh.com/account/edit_proxies/

You need to have at least a 20 plan, so that more than one server will be available for selection.

The maximum number of proxies you can check depends upon your plan. Proxies that you do not have access to are disabled.

  1. Use the Make Custom PAC File link to access the screen listing all the proxies you selected on your dashboard.
  2. These are unchecked on the Make Custom PAC File screen.
  3. On this screen, select only the proxies that you want to include in your .pac file.
  4. Then click the Make PAC button. The system will return a message that shows the resulting .pac file near the bottom of the page.
  5. For example: "Here is a link to your PAC file: https://d1tzjzeluf7kb7.cloudfront.net/pacs/us-il_us-wa.pac"

A .pac filename takes the names of the servers listed in the file, e.g., us-ca_us-tx.pac.

To return to the dashboard, click the Back button or click the Dashboard link on the ribbon.

Further Information

For more about .pac files, please see Advantages of a Proxy Auto-Configuration (PAC) File on our blog site, proxyserver.com.

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