Server-Side Browser Detection and Content Delivery : Mobile Detection (part 2) - Detecting the Context

1/29/2011 6:45:49 PM

2. Detecting the Context

We’ve already seen how the network protocol works, and what information is provided and not provided in a mobile browser request. Now let’s get some data and information from the context.

2.1. How to read a header

The specifics depend on the language, but all server-side platforms offer a way to read the request’s header. Some languages use the same header as the parameter (for example, Accept-Charset), and others use a larger version with the syntax HTTP_X, where X is the header name in all uppercase and with the - replaced by _HTTP_ACCEPT_CHARSET). (for example,


Some Nokia devices expose a custom HTTP header that defines the connection type. The header is x-nokia-musicshop-bearer and the possible values are WLANGPRS/3G. We can try to read this header and, if it exists, get more information about the context. or

In Java Servlets or JSP, we read a header using:


In ASP 3, we use this:


And in PHP:


In ASP.NET with C# or Visual Basic, we have a Headers collection and public members for most of the common headers:

// This is the C# version

' This is the VB version


These devices also expose a custom HTTP via header that can be used to see which browser is being used. For example, if the value contains an MDS string, the user may be connected via the BlackBerry Browser through the corporate server; if it contains BISB the user is using the Internet Browser connecting through the carrier; and if the value is not defined, the user may be using the WiFi Hotspot Browser.

2.2. How to read the IP address

The IP address from which the request originated can be read with the following code:

// In Java
String address = req.getRemoteAddr();

// In PHP
$address = $_SERVER["REMOTE_ADDR"];

// In C#
String address = Request.UserHostAddress;

What we can do with the IP address? We need to get an updated list of the IP ranges assigned to each carrier. The carriers distribute this information to their partners, and it can also be found in forums and communities or through commercial services.


Massive’s Operator Identification Platform is a community-based database service that allows us to determine visitors’ countries and network operators, if detected, using a simple HTTP service request. You can request an account at It is free for noncommercial sites, and commercial licenses start at $10 per month.

2.3. Opera Mini

As mentioned earlier, there are some proxied browsers on the market (Opera Mini is the most widely installed), and we need to take care of differences in the headers in such browsers. Even on a well-known device, such as a BlackBerry or a Nokia N97, if Opera Mini is in use the requests we receive on our servers will come from the Opera Mini proxy and not from the device itself. So, the client IP address will be Opera’s server address, and the user-agent string will be the proxy’s one. On any device, the Opera Mini 5 user-agent string looks like this:

Opera/9.80 (J2ME/MIDP; Opera Mini/5.0.16823/1126; U; en) Presto/2.2.0

Fortunately, Opera Mini offers the original IP address and the original user-agent string, along with other information, in new headers (listed in Table 10-2) that we can read using the techniques we have already seen.


Opera Mini has a developer site at that offers tips and technical information about Opera Mini website development. Other intermediates are not as developer-friendly as Opera Mini and remove all the original headers, so we are blind in detecting the device and its origin.

Table 2. Opera Mini additional HTTP headers
X-OperaMini-Phone-UAProvides the user-agent string identifying the device that downloaded the Opera Mini client (or the current device’s user-agent string if not available).
X-OperaMini-PhoneProvides the device’s brand and model, separated by a hash (<brand>#<model>).
X-Forwarded-ForProvides a CSV list of all the proxy servers in the chain that have forwarded the request from the device to Opera Mini’s proxy. Opera recommends using the last IP address listed for geolocation purposes.
X-OperaMini-FeaturesProvides a CSV list of phone features, from the following list:
  • basic (Java MIDP 1.0 device, low resources)

  • advanced (Java MIDP 2.0 device, high resources)

  • camera (camera detected, so we can provide a file upload input for pictures)

  • file_system (Java filesystem support detected, so the user can download and upload files)

  • folding (content folding option is enabled)

  • secure (connection between phone and proxy is encrypted)


Content folding in Opera Mini refers to the ability of the browser to group a series of links into a menu that can be closed and opened to gain space on the screen.

2.4. Mobile detection

If you only want to know whether the user is browsing from a desktop or a mobile device (perhaps for doing a redirection), the quickest way to find out is to check for some different well-known strings (iPhone, iPod, Nokia, etc.) inside the User-Agent header. Based on their presence or absence, you can make an educated guess about whether or not the user is on a mobile device.


There is an excellent collection of mobile-specific User-Agent headers at

Andy Moore has developed a very simple but powerful PHP script for detecting mobile user agents and browsers. The latest version (free for non-profit purposes) can be downloaded from

You can find similar scripts in different languages at


Some devices support multipart document delivery. A multipart document includes XHTML and resources (images, CSS) in the same HTTP response, enhancing the download performance. To determine whether a device supports multipart documents, check for the multipart/mixed or application/vnd.wap.multipart MIME type in the Accept header. Visit for more information.
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