Automatic Detection

Using automatic detection

You can configure your network so that Internet Explorer 9 is automatically customized the first time a user starts it. This can reduce administrative overhead and help-desk calls related to users' browser settings.

Automatic detection is based on Web Proxy AutoDiscovery (WPAD). It is supported by Dynamic Host Configuration Protocol (DHCP) and Domain Name System (DNS). If you select appropriate settings, DHCP and DNS servers can automatically detect and configure browser settings by directing Internet Explorer 9 to the location of a configuration file. This feature builds on existing automatic configuration technologies, in which a browser can be configured from a central location with an automatic proxy script file (.wpad or .pac file).

With automatic detection, Internet Explorer 9 can be automatically configured when it is started. This is true even if the browser was not originally customized and deployed by the administrator. For example, automatic detection can automatically configure and customize an Internet Explorer 9 browser that a user downloads independently from the Internet.

To enable automatic detection, in Internet Explorer Administration Kit 9 tools or Internet Explorer Maintenance, select Automatic Browser Configuration, and then select the Automatically detect configuration settings check box.

Configuring servers for automatic detection

To implement automatic detection, you must configure specific settings on DHCP servers, DNS servers, or both.

  • A DHCP server enables you to specify global and subnet TCP/IP parameters centrally, and to define users' parameters by using reserved addresses. When a user's computer is moved between subnets, it is automatically reconfigured for TCP/IP when the computer is started.

  • DNS is a set of protocols and services on a TCP/IP network that allow users to search for other computers by using hierarchical, user-friendly names (hosts), instead of numeric IP addresses.

DHCP servers with automatic detection work best for local area network (LAN)–based users, because these servers provide faster access to LAN users and greater flexibility for specifying configuration files. DNS servers with automatic detection work best for dial-up connections, although they are also capable of handling network connections.


DHCP has a higher priority for automatic detection than DNS. If DHCP provides the URL for a .pac, .jvs, .js, or .ins configuration file, then no DNS lookup is performed.

Automatic detection for DHCP

To set up automatic detection on DHCP servers, you must create a new option type with the code number 252. Then associate (with this option type) the URL to your configuration file. This file can be a .pac configuration file.

For more information about configuring option types for automatic detection, consult your server documentation.


Your DHCP servers must support the DHCPINFORM message.

Automatic detection for DNS

In the DNS database file, enter a host record named wpad that contains the IP address of the web server that contains the .pac, .jvs, .js, or .ins automatic configuration file. Alternatively, enter a canonical name (CNAME) alias record named wpad that contains the resolved name (not the IP address) of the server that contains the .pac automatic configuration file.

For more information about configuring a host record or CNAME alias record in the DNS database file, consult your server documentation.

After the record is added and the database file is propagated to the server, the DNS name wpad.<domain>.com resolves to the same name as your server that contains the automatic configuration file.


When using DNS, Internet Explorer 9 constructs a default URL template based on the host name wpad. For example: http://wpad.<domain>.com/wpad.dat. Therefore, in the web server wpad record, you must set up a file or redirection point named Wpad.dat to deliver the contents of your automatic configuration file.