Proxy Auto-Configuration URL – ProxyMesh Knowledge Base
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, 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 auto-configuration function will work as both a 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 configuration, Autoconfiguration URL, Automatic 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 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 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:
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.
Use the Make Custom PAC File link to access the screen listing all the proxies you selected on your dashboard.
These are unchecked on the Make Custom PAC File screen.
On this screen, select only the proxies that you want to include in your file.
Then click the Make PAC button. The system will return a message that shows the resulting file near the bottom of the page.
For example: “Here is a link to your PAC file:
A filename takes the names of the servers listed in the file, e. g.,
To return to the dashboard, click the Back button or click the Dashboard link on the ribbon.
Further Information
For more about
files, please see
Advantages of a Proxy Auto-Configuration (PAC) File on our blog site,
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Last updated on September 30, 2021
Proxy Auto-Config URL – Thunderstone Tech Support | Search …
Syntax: the full URL to a proxy auto-config (PAC) script
This specifies the URL to a PAC script. The script is fetched once at
the start of a walk, and then run for each URL walked, to determine
the proxy (or direct fetch) to use for that URL. This setting
overrides Proxy.
A proxy auto-config script can be used to dynamically configure the
proxy to use on a URL-by-URL basis, instead of using one proxy for all
URLs. The script can also return multiple proxies to use; e. g. a
primary, and fallback(s) to use if the primary is unreachable. See
the website for more information on PAC
scripts.
In Windows Control Panel, the Internet Options →
Connections tab → LAN settings →
Use automatic configuration script address value is equivalent
to the Search Appliance’s Proxy Auto-Config URL setting.
Copyright © Thunderstone Software Last updated: Jun 21 2021
How to disable automatic proxy caching in Internet Explorer
Internet Explorer 11 Internet Explorer 10 Internet Explorer 9 Windows 7 Enterprise Windows 7 Enterprise N Windows 7 Home Basic Windows 7 Home Premium Windows 7 Professional Windows 7 Professional N Windows 7 Starter Windows 7 Starter N Windows 7 Ultimate Windows 7 Ultimate N Microsoft Windows XP Home Edition Microsoft Windows XP Professional Microsoft Windows XP Tablet PC Edition Microsoft Windows XP Professional x64 Edition
Note: The Internet Explorer 11 desktop application will be retired and go out of support on June 15, 2022 (for a list of what’s in scope, see the FAQ). The same IE11 apps and sites you use today can open in Microsoft Edge with Internet Explorer mode. Learn more here.
Summary
When you configure Internet Explorer to use an automatic proxy configuration script, it caches the proxy that is returned by the FindProxyForURL call. The caching mechanism (Automatic Proxy Result Cache) is performed on a host basis (that is, not on an URL basis). This prevents you from using different proxies to gain access to the same Web server. The following sample scenario demonstrates this behavior:
Configure a Web server that is named “Webserver” with two virtual folders: “/login” and “/test”.
Create the following PAC file:
function FindProxyForURL (url, host){if shExpMatch (url, “webserver/login”) return “DIRECT”;else return “PROXY myproxy:80; PROXY mybackupproxy:80”;}
Configure Internet Explorer to use this PAC file.
Start Internet Explorer and type the following Web address:
webserver/loginInternet Explorer loads the PAC file and correctly uses a direct connection.
When the logon page appears, type webserver/test. If you use Network Monitor, you can observe that access to “webserver/test” still uses a direct connection instead of one of the returned proxies.
More Information
The Automatic Proxy Result Cache is a performance enhancement that was added to Internet Explorer 5. 5 and later. The purpose of the cache is to reduce the client-side processing of the automatic proxy configuration script. When you connect to an Internet site, the FindProxyForURL function is used to determine whether a proxy should be used and which proxy to use. Internet Explorer 5. 5 and later first checks the Automatic Proxy Result Cache to determine whether a proxy was used to connect to the host on previous attempts. If this checks fails, it indicates that this is the first attempt to connect to the host during the current session and the normal proxy detection logic applies. If an automatic proxy configuration script is configured to be used and Internet Explorer is able to retrieve it from the network (either if the Automatically Detect Settings option or the Use automatic configuration script are enabled), the Automatic Proxy Result Cache is updated with the hostname being accessed and the complete set of proxy servers returned by parsing the script. In the example, any hostname that is determined to use a proxy server will have “PROXY myproxy:80; PROXY mybackupproxy:80” added to the Automatic Proxy Result this scenario, “myproxy” is used for any subsequent access to a cached hostname and the automatic proxy configuration script is not re-processed. If “myproxy” is suddenly inaccessible, the following happens:
The “myproxy” proxy is added to the list of bad proxy servers.
The “mybackupproxy” proxy is selected to serve the request for the hostname in question, taken from the Automatic Proxy Result Cache.
If the connection is successful, “mybackupproxy” is used in subsequent requests to this hostname during the same browsing session.
If all of the proxy servers returned from the automatic proxy configuration script are inaccessible, then you receive a “Page Cannot Be Displayed” error message in Internet Explorer (which would happen if a static proxy server is suddenly inaccessible) allows proxy failover to still occur even if the Automatic Proxy Result Cache is enabled but it does not allow you to specify a different proxy server for the same hostname but, for instances, for different URL’s, as illustrated in the example. If this is a requirement, then you may want to disable the Automatic Proxy Result Cache feature. This will result in client-side processing of every GET request that is issued by Internet Explorer. As a result, Internet Explorer performance may be impacted depending on the logic of the Automatic Proxy Configuration Script and its size. To disable the Automatic Proxy Result Cache, use one of the following If you disable automatic proxy caching, Internet Explorer performance may be affected.
Method 1: Modify the registry
Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:
322756 How to back up and restore the registry in WindowsYou can disable the Automatic Proxy Result Cache by using the following registry key:
HKEY_CURRENT_USER\Software\Policies\Microsoft\Windows\CurrentVersion\Internet Settings
Value: EnableAutoproxyResultCacheType: REG_DWORDData value: 0 = disable caching; 1 (or key not present) = enable automatic proxy caching (this is the default behavior)If the registry key is not present, you can create the registry key by using the following registry file:
Windows Registry Editor Version 5. 00[HKEY_CURRENT_USER\Software\Policies\Microsoft\Windows\CurrentVersion\Internet Settings]”EnableAutoProxyResultCache”=dword:00000000″
Method 2: Modify Group Policy settings
Click Start, click Run, type, and then click OK.
In Group Policy Object Editor, double-click User Configuration\Administrative Templates\Windows Components\Internet Explorer.
Double-click Disable caching of Auto-Proxy scripts.
Click Enable, and then click OK.
You may have to use this registry key if you connect by using a proxy server that is handling secure and non-secure requests on the same server. One example of this behavior is the SQUID Proxy Server software. Because Internet Explorer typically caches port information, it may not send a secure request over the correct port number when it tries to send secure and non-secure responses to the same server, but on different port more information about the addition of the bad proxy server list, click the following article number to view the article in the Microsoft Knowledge Base:
320507 Internet Explorer does not retry bad proxy server for 30 minutes
Frequently Asked Questions about auto proxy configuration url
Where is the auto proxy configuration URL?
In Windows Control Panel, the Internet Options → Connections tab → LAN settings → Use automatic configuration script address value is equivalent to the Search Appliance’s Proxy Auto-Config URL setting.
How do I remove automatic proxy configuration URL?
Click Start, click Run, type gpedit. msc, and then click OK. In Group Policy Object Editor, double-click User Configuration\Administrative Templates\Windows Components\Internet Explorer. Double-click Disable caching of Auto-Proxy scripts.
What is a proxy PAC URL?
A Proxy Auto-Configuration (PAC) file is a JavaScript function that determines whether web browser requests (HTTP, HTTPS, and FTP) go directly to the destination or are forwarded to a web proxy server. The JavaScript function contained in the PAC file defines the function: function FindProxyForURL(url, host) { // … }Aug 13, 2021