Use proxy auto-configuration (.pac) files with IEAK 11

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Caution

Update: The retired, out-of-support Internet Explorer 11 desktop application has been permanently disabled through a Microsoft Edge update on certain versions of Windows 10. For more information, see Internet Explorer 11 desktop app retirement FAQ.

These are various ways you can use a proxy auto-configuration (.pac) file to specify an automatic proxy URL. We've included some examples here to help guide you, but you'll need to change the proxy names, port numbers, and IP addresses to match your organization's info.

Included examples:

Example 1: Connect directly if the host is local

In this example, if the host is local, it can connect directly. However, if the server isn't local, it must connect through a proxy server. Specifically, the isPlainHostName function looks to see if there are any periods (.) in the host name. If the function finds periods, it means the host isn’t local and it returns false. Otherwise, the function returns true.

function FindProxyForURL(url, host)
 {
 if (isPlainHostName(host))
 return "DIRECT";
 else
 return "PROXY proxy:80";
 }

Example 2: Connect directly if the host is inside the firewall

In this example, if the host is inside the firewall, it can connect directly. However, if the server is outside the firewall, it must connect through a proxy server. Specifically, the localHostOrDomainIs function only runs for URLs in the local domain. If the host domain name matches the provided domain information, the dnsDomainIs function returns true.

function FindProxyForURL(url, host)
 {
 if ((isPlainHostName(host) ||
 dnsDomainIs(host, ".company.com")) &&
 !localHostOrDomainIs(host, "www.company.com") &&
 !localHostOrDoaminIs(host, "home.company.com"))
 return "DIRECT";
 else
 return "PROXY proxy:80";
}

Example 3: Connect directly if the host name is resolvable

In this example, if the host name can be resolved, it can connect directly. However, if the name can’t be resolved, the server must connect through a proxy server. Specifically, this function requests the DNS server to resolve the host name it's passed. If the name can be resolved, a direct connection is made. If it can't, the connection is made using a proxy. This is particularly useful when an internal DNS server is used to resolve all internal host names.

Important
The isResolvable function queries a Domain Name System (DNS) server. References to Object Model objects, properties, or methods cause the proxy auto-configuration file to fail silently. For example, the references window.open(...), alert(...), and password(...) all cause the proxy auto-configuration file to fail.

function FindProxyForURL(url, host)
 {
 if (isResolvable(host))
 return "DIRECT";
 else
 return "PROXY proxy:80";
 }

Example 4: Connect directly if the host is in specified subnet

In this example, if the host is in a specified subnet, it can connect directly. However, if the server is outside of the specified subnet, it must connect through a proxy server. Specifically, the isInNet (host, pattern, mask) function returns true if the host IP address matches the specified pattern. The mask indicates which part of the IP address to match (255=match, 0=ignore).

Important
The isInNet function queries a DNS server. References to Object Model objects, properties, or methods cause the proxy auto-configuration file to fail silently. For example, the references window.open(...), alert(...), and password(...) all cause the proxy auto-configuration file to fail.

function FindProxyForURL(url, host)
 {
 if (isInNet(host, "999.99.9.9", "255.0.255.0"))
 return "DIRECT";
 else
 return "PROXY proxy:80";
 }

Example 5: Determine the connection type based on the host domain

In this example, if the host is local, the server can connect directly. However, if the host isn’t local, this function determines which proxy to use based on the host domain. Specifically, the shExpMatch(str, shexp) function returns true if str matches the shexp using shell expression patterns. This is particularly useful when the host domain name is one of the criteria for proxy selection.

function FindProxyForURL(url, host)
 {
 if (isPlainHostName(host))
 return "DIRECT";
 else if (shExpMatch(host, "*.com"))
 return "PROXY comproxy:80";
 else if (shExpMatch(host, "*.edu"))
 return "PROXY eduproxy:80";
 else
 return "PROXY proxy";
 }

Example 6: Determine the connection type based on the protocol

In this example, the in-use protocol is extracted from the server and used to make a proxy selection. If no protocol match occurs, the server is directly connected. Specifically the substring function extracts the specified number of characters from a string. This is particularly useful when protocol is one of the criteria for proxy selection.

function FindProxyForURL(url, host)
 {
 if (url.substring(0, 5) == "http:") {
 return "PROXY proxy:80";
 }
 else if (url.substring(0, 4) == "ftp:") {
 return "PROXY fproxy:80";
 }
 else if (url.substring(0, 6) == "https:") {
 return "PROXY secproxy:8080";
 }
 else {
 return "DIRECT";
      }
 }

Example 7: Determine the proxy server based on the host name matching the IP address

In this example, the proxy server is selected by translating the host name into an IP address and then comparing the address to a specified string.

Important 
The dnsResolve function queries a DNS server. References to Object Model objects, properties, or methods cause the proxy auto-configuration file to fail silently. For example, the references window.open(...), alert(...), and password(...) all cause the proxy auto-configuration file to fail.

function FindProxyForURL(url, host)
 {
 if (dnsResolve(host) == "999.99.99.999") { // = https://secproxy
 return "PROXY secproxy:8080";
 }
 else {
 return "PROXY proxy:80";
 }
 }

Example 8: Connect using a proxy server if the host IP address matches the specified IP address

In this example, the proxy server is selected by explicitly getting the IP address and then comparing it to a specified string. If no protocol match occurs, the server makes a direct connection. Specifically, the myIpAddress function returns the IP address (in integer-period format) for the host that the browser is running on.

function FindProxyForURL(url, host)
 {
 if (myIpAddress() == "999.99.999.99") { 
 return "PROXY proxy:80";
 }
 else {
 return "DIRECT";
 }
 }

Example 9: Connect using a proxy server if there are periods in the host name

In this example, the function looks to see if there are periods (.) in the host name. If there are any periods, the connection occurs using a proxy server. If there are no periods, a direct connection occurs. Specifically, the dnsDomainLevels function returns an integer equal to the number of periods in the host name.

Note
This is another way to determine connection types based on host name characteristics.

function FindProxyForURL(url, host)
 {
 if (dnsDomainLevels(host) > 0) { // if the number of periods in host > 0
 return "PROXY proxy:80";
 }
 return "DIRECT";
 }

Example 10: Connect using a proxy server based on specific days of the week

In this example, the function decides whether to connect to a proxy server, based on the days of the week. Connecting on days that don’t fall between the specified date parameters let the server make a direct connection. Specifically the weekdayRange(day1 [,day2] [,GMT] ) function returns whether the current system time falls within the range specified by the parameters day1, day2, and GMT. Only the first parameter is required. The GMT parameter presumes time values are in Greenwich Mean Time rather than the local time zone. This function is particularly useful for situations where you want to use a proxy server for heavy traffic times, but allow a direct connection when traffic is light.

function FindProxyForURL(url, host)
 {
 if(weekdayRange("WED", "SAT", "GMT")) 
 return "PROXY proxy:80";
 else 
 return "DIRECT";
 }