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Published: Thursday, December 14, 2000

Obtaining your User's Browser Information


There are a number of ways to gather information about your user's browser, and there are a number of reasons you may want to. Some sites may have content that requires Internet Explorer only, or requires at least version 4.0 of either Netscape or IE. In either case, there are a number of techniques you can use to obtain browser information. In this article we'll examine four methods:

    - continued -

  • Using client-side script
  • Using the User-Agent server variable
  • Using the Browser Capabilities component
  • Using a third-party program

Using Client-Side Script
There are a number of server-side techniques that can be used to determine what browser a user is visiting with. Sometimes, though, a server-side solution is not ideal; perhaps you'd like to have an HTML page (non-ASP page) be able to determine the type of browser and automatically redirect the user to an appropriate page. Fortunately, there is a client-side scripting technique to determine a user's browser, but, for this to work, the user must have JavaScript support enabled. (For an article on how to determine if a user has client-side JavaScript support enabled in her browser, check out: Determining if your Visitors have JavaScript and Cookies Enabled.)

In client-side JavaScript code, the navigator object reveals information about the user's browser. There are a number of properties for thie navigator object, the important ones being: appName, appVersion, and platform. appName returns the name of the browser (such as "Microsoft Internet Explorer"); appVersion returns the version of the browser; and platform returns the user's platform ("Win16", "Win32", etc.).

A simple example of client-side JavaScript code that lists the browser type, version, and platform can be seen below:

<script language="JavaScript">
<!--
document.write("<b>Browser:</b> " + navigator.appName);
document.write("<br><b>Version:</b> " + navigator.appVersion);
document.write("<br><b>Platform:</b> " + navigator.platform);
// -->
</script>

The output of this code can be seen below:

You can then make a decision on where to redirect the user based on this information. For example, say that you had both a Netscape-friendly site and an IE-friendly site. To accomplish this, you could use code like:

<script language="JavaScript">
<!--
if (navigator.appName == "Microsoft Internet Explorer")
  window.location = "/IESite/";
else
  window.location = "/NetscapeSite/";
// -->
</script>

For more information on client-side JavaScript routines on browser detection and redirection, be sure to check out Browser-Specific JavaScripts. There are numerous other JavaScript articles that can do all sorts of neat things at sites like Doc JavaScripts and The JavaScript Source.

Using the User-Agent Server Variable
When a browser makes a request to a Web page on a server, it sends along with that request a number of headers, commonly referred to as request headers, or HTTP headers. (For more information on HTTP headers, be sure to check out: Accessing HTTP Headers and Environment Variables!) One of these headers is the User-Agent header, which is a string containing detailed information about the visitor's browser version and type. To display this HTTP header from an ASP page, simply use the following code:

<% Response.Write Request.ServerVariables("HTTP_USER_AGENT") %>

The output of the above code can be seen below:
CCBot/2.0 (http://commoncrawl.org/faq/)

Note that this string is overflowing with information, as you can probably tell. It may seem hard to pick out the browser type, a quick check for the characters "MSIE" should let us know if it's Internet Explorer or not.

If InStr(1, Request.ServerVariables("HTTP_USER_AGENT"), "MSIE") then
  Response.Write "You are using Internet Explorer"
Else
  Response.Write "You are <b>not</b> using Internet Explorer"
End If

Clearly these first two methods (client-side script and the User-Agent string) are really poor ways for determining a user's browser and version. They're quick and efficient, but you cannot obtain any sort of detailed information without picking through these strings and extracting various bits of information. In Part 2 we'll examine two other approaches, ones that offer much more detailed information about the user's browser in an easier-to-obtain format.

  • Read Part 2!


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