How do I detect what browser is used to access my site?

Question

How do I detect what browser (IE, Firefox, Opera) the user is accessing my site with? Examples in Javascript, PHP, ASP, Python, JSP, and any others you can think of would be helpful. Is there a language agnostic way to get this information?

Answer 1

If it's for handling the request, look at the User-Agent header on the incoming request.

UPDATE: If it's for reporting, configure your web server to log the User-Agent in the access logs, then run a log analysis tool, e.g., AWStats.

UPDATE 2: FYI, it's usually (not always, usually) a bad idea to change the way you're handling a request based on the User-Agent.

Answer 2

Comprehensive list of User Agent Strings from various Browsers

The list is really large :)

Answer 3

You would take a look at the User-Agent that they are sending. Note that you can send whatever agent you want, so that's not 100% foolproof, but most people don't change it unless there's a specific reason to.

Answer 4

A quick and dirty java servlet example

private String getBrowserName(HttpServletRequest request) {
    // get the user Agent from request header
    String userAgent = request.getHeader(Constants.BROWSER_USER_AGENT);
    String BrowesrName = "";
    //check for Internet Explorer
    if (userAgent.indexOf("MSIE") > -1) {
        BrowesrName = Constants.BROWSER_NAME_IE;
    } else if (userAgent.indexOf(Constants.BROWSER_NAME_FIREFOX) > -1) {
        BrowesrName = Constants.BROWSER_NAME_MOZILLA_FIREFOX;
    } else if (userAgent.indexOf(Constants.BROWSER_NAME_OPERA) > -1) {
        BrowesrName = Constants.BROWSER_NAME_OPERA;
    } else if (userAgent.indexOf(Constants.BROWSER_NAME_SAFARI) > -1) {
        BrowesrName = Constants.BROWSER_NAME_SAFARI;
    } else if (userAgent.indexOf(Constants.BROWSER_NAME_NETSCAPE) > -1) {
        BrowesrName = Constants.BROWSER_NAME_NETSCAPE;
    } else {
        BrowesrName = "Undefined Browser";
    }
    //return the browser name
    return BrowesrName;
}

Answer 5

You can use the HttpBrowserCapabilities Class in ASP.NET. Here is a sample from this link

private void Button1_Click(object sender, System.EventArgs e)
{
        HttpBrowserCapabilities bc;
        string s;
        bc = Request.Browser;
        s= "Browser Capabilities" + "\n";
        s += "Type = " + bc.Type + "\n";
        s += "Name = " + bc.Browser + "\n";
        s += "Version = " + bc.Version + "\n";
        s += "Major Version = " + bc.MajorVersion + "\n";
        s += "Minor Version = " + bc.MinorVersion + "\n";
        s += "Platform = " + bc.Platform + "\n";
        s += "Is Beta = " + bc.Beta + "\n";
        s += "Is Crawler = " + bc.Crawler + "\n";
        s += "Is AOL = " + bc.AOL + "\n";
        s += "Is Win16 = " + bc.Win16 + "\n";
        s += "Is Win32 = " + bc.Win32 + "\n";
        s += "Supports Frames = " + bc.Frames + "\n";
        s += "Supports Tables = " + bc.Tables + "\n";
        s += "Supports Cookies = " + bc.Cookies + "\n";
        s += "Supports VB Script = " + bc.VBScript + "\n";
        s += "Supports JavaScript = " + bc.JavaScript + "\n";
        s += "Supports Java Applets = " + bc.JavaApplets + "\n";
        s += "Supports ActiveX Controls = " + bc.ActiveXControls + "\n";
        TextBox1.Text = s;
}

Answer 6

PHP's predefined superglobal array $_SERVER contains a key "HTTP_USER_AGENT", which contains the value of the User-Agent header as sent in the HTTP request. Remember that this is user-provided data and is not to be trusted. Few users alter their user-agent string, but it does happen from time to time.

Answer 7

On the client side, you can do this in Javascript using the navigation.userAgent object. Here's a crude example:

if (navigator.userAgent.indexOf("MSIE") > -1) 
{
    alert("Internet Explorer!");
}
else if (navigator.userAgent.indexOf("Firefox") > -1)
{
    alert("Firefox!");
}

A more detailed and comprehensive example can be found here: http://www.quirksmode.org/js/detect.html

Note that if you're doing the browser detection for the sake of Javascript compatibility, it's usually better to simply use object detection or a try/catch block, lest some version you didn't think of slip through the cracks of your script. For example, instead of doing this...

if(navigator.userAgent.indexOf("MSIE 6") > -1)
{
    objXMLHttp = new ActiveXObject("Microsoft.XMLHTTP");
}
else
{
    objXMLHttp = new XMLHttpRequest();
}

...this is better:

if(window.XMLHttpRequest) // Works in Firefox, Opera, and Safari, maybe latest IE?
{
    objXMLHttp = new XMLHttpRequest();
}
else if (window.ActiveXObject) // If the above fails, try the MSIE 6 method
{
    objXMLHttp = new ActiveXObject("Microsoft.XMLHTTP");
}

Answer 8

It may be dependent of your setting. With apache on linux, its written in the access log /var/log/apache2/access_log

Answer 9

You can do this by:
- looking at the web server log, OR
- looking at the User-Agent field in the HTML request (which is a plain text stream) before processing it.

Answer 10

First of all, I'd like to note, that it is best to avoid patching against specific web-browsers, unless as a last result -try to achieve cross-browser compatibility instead using standard-compliant HTML/CSS/JS (yes, javascript does have a common denominator subset, which works across all major browsers).

With that said, the user-agent tag from the HTTP request header contains the client's (claimed) browser. Although this has become a real mess due to people working against specific browser, and not the specification, so determining the real browser can be a little tricky.

Match against this:

contains browser

Firefox -> Firefox

MSIE -> Internet Explorer

Opera -> Opera (one of the few browsers, which don't pretend to be Mozilla :) )

Most of the agents containing the words "bot", or "crawler" are usually bots (so you can omit it from logs / etc)

Answer 11

check out browsecap.ini. The linked site has files for multiple scripting languages. The browsecap not only identifies the user-agent but also has info about the browser's CSS support, JS support, OS, if its a mobile browser etc.

cruise over to this page to see an example of what info the browsecap.ini can tell you about your current browser.