HOWTO: Determining Browser Version from a Script

ID: Q167820

The information in this article applies to:

SUMMARY

With the new features that Internet Explorer 4.0 provides, it may be desirable for both client-side and server-side scripts to determine the browser version, so that a Web application can either take advantage of new functionality, or degrade gracefully, depending on the version of the currently-running browser.


MORE INFORMATION

From a Client-Side Script

The JScript function below can be used to determine the version of the browser it is running on from a client-side script. The function runs on the large majority of browsers currently available and returns the major version number for any Microsoft Internet Explorer browser, and zero (0) for others. Use of this function assures that the script will be compatible with future versions of the Internet Explorer. 

   // This function returns Internet Explorer's major version number,
   // or 0 for others. It works by finding the "MSIE " string and
   // extracting the version number following the space, up to the decimal
   // point, ignoring the minor version number
   <SCRIPT LANGUAGE="JavaSCRIPT">
   function msieversion()
   {
      var ua = window.navigator.userAgent
      var msie = ua.indexOf ( "MSIE " )

      if ( msie > 0 )      // If Internet Explorer, return version number
         return parseInt (ua.substring (msie+5, ua.indexOf (".", msie )))
      else                 // If another browser, return 0
         return 0

   }
   </SCRIPT>
When checking version numbers, scripts should always use the >= operator, instead of the = operator to ensure compatibility with future versions. Existing scripts that specifically check for userAgent equal to "MSIE 3," for instance, should be changed to use the >= operator so that the scripts recognize Internet Explorer 4.0 as well.

The following example demonstrates how to detect the browser version from a client-side script. Note that this example does not specifically check for platform version, such as Windows 95, Windows NT, Windows 3.1, and so forth, which require a separate userAgent substring check when applicable: 

<SCRIPT LANGUAGE="javascript">
   if ( msieversion() >= 4 )

      document.write ( "This is Internet Explorer 4 or later" );

   else if ( msieversion() >= 3 )

      document.write ( "This is Internet Explorer 3" );

   else

      document.write ( "This is another browser" );

   </SCRIPT>

From a Server-Side Script

The Browser Capability component that comes with Active Server Pages (ASP) provides your scripts with a description of the capabilities of the client's Web browser by comparing the User-Agent HTTP Header with the entries in the BROWSCAP.INI file. In order for an ASP application to detect the browser's support for the new Internet Explorer 4.0 features, copy the latest BROWSCAP.INI from one of the following locations:
http://www.cyscape.com/asp/browscap/

http://www.microsoft.com/backoffice/downloads/moreinfo/bcf.asp
Copy it to your %windows%\system32\inetsrv\asp\cmpnts directory and execute a server-side script similar to the example below.

This example specifically takes advantage of new Dynamic HTML functionality if the current browser is Internet Explorer 4.0 or later: 

<HTML>
<BODY>

   <%  Set bc = Server.CreateObject("MSWC.BrowserType") %>
   <table border=0 cellspacing="0" cellpadding="5">

      <tr>

         <% If bc.browser = "IE" and bc.version >= 4 Then %>
         <td><a href="chocolate.htm" TARGET="_TEXT"
              onmouseover="this.style.color='red'"
              onmouseout="this.style.color='purple'">chocolate</a>
         </td>

         <% Else %>
            <td><a href="chocolate.htm" TARGET="_TEXT">chocolate</a></td>
         <% End If %>

         <td>|</td>

         <% If bc.browser = "IE" and bc.version >= 4 Then %>
         <td><a href="vanilla.htm" TARGET="_TEXT"
              onmouseover="this.style.color='red'"
              onmouseout="this.style.color='purple'">vanilla</a>
         </td>

         <% Else %>
            <td><a href="vanilla.htm" TARGET="_TEXT">vanilla</a></td>
         <% End If %>

      </tr>

   </table>

</BODY>
</HTML>


REFERENCES

Components Reference in the Active Server Pages (ASP) Roadmap

Additional query words: detect verify check 


Keywords          : kbIE300 kbIE301 kbIE400 kbIE302 
Version           : WINDOWS:3.0,3.01,3.02,4.0
Platform          : WINDOWS 
Issue type        : kbhowto

Last Reviewed: March 26, 1999