What is a User Agent string, also known as your Browser string? Well it's basically your computer's information as far as what software you are running. It just gives the basics as to which OS (operating system) you are running, your basic security (if you have any) and which internet browser you are using. It also may tell if some other applications are installed, like the Microsoft.NET framework and the version you have installed.

Sometimes 3rd party programs will also inject some sort of tag in it to show that you are running their software as well. The Google Toolbar adds a small "GTB6" tag for example.

Why does your browser give away this information? Some websites may make use of it to help them show you certain pages optimized for your particular setup, is one example. In general, it is used by websites simply to enhance the user experience in one way or another. It can be used to help identify you, but generally not without some sort of other useful information, such as your IP address, since thousands, or hundreds of thousands of users may have the same exact User Agent string as you do.

How do you find your User Agent String? Go to IPCHICKEN

Here is a great site that will help you read user agent strings: CLICK

Here are some examples:

My main computer at home:
On ipchicken it will be the last line where it starts off as Browser. ipchicken reads mine as:
Browser: Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv:1.9.1.7) Gecko/20091221 Firefox/3.5.7

User Agent String explained:

Here is what it shows from my iPod touch (it would look almost the same from a iphone)

When I go to ipchicken it shows: Browser: Mozilla/5.0 (iPod; U; CPU iPhone OS 3_1_2 like Mac OS X; en-us) AppleWebKit/528.18 (KHTML, like Gecko) Version/4.0 Mobile/7D11 Safari/528.16

User Agent String explained:

Here is my archos media table:
Browser: Opera/9.02 (Linux armv 7l; U; ARCHOS; GOGl; mobile; G6H; Version 1.0.87 (WMDRMPD: 10.1); en)

User Agent String explained:

Trackers and websites use useragent strings to help identify the person. You can go to a proxy site but in the end your user string will stay the same. There is an extension for Firefox to change your UserAgent string on the fly named UserAgent Switcher.

There are many lists on the internet where you can find some UserAgent Strings to add to the list of UserAgents to switch between. For example, here.

Some fun tricks can be done when playing with UserAgent Strings. Want to see how a website might look strictly to a GoogleBot? Some websites optimize their pages to show only a certain page if it detects a GoogleBot, just copy the GoogleBot user agent string to your UserAgent Switcher and select it, then load the page.

There have also been some tricks to bypass password protected sites or pages by masquerading as a search engine crawler by using a search engine's UserAgent String, although in general, this isn't usually likely to happen.

Know of any other cool tricks by fiddling with UserAgent Strings? Let us know in a comment!

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