User-Agent String

The browser that spearheaded the popularity of the Web was Netscape Navigator 3.0,which was released around 1996. The code name of the Netscape engine was Mozilla, and the user-agent string had a very simple format:

Mozilla/AppVersion (Platform; Security [; OS-or-CPU-Description])

 

In order to fully understand exactly what is going on, take a look at an example from Netscape 6.2.1 running on Windows XP:
Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:0.9.4) Gecko/20011128
Netscape6/6.2.1
Matching up the various pieces of information:
❑ MozillaVersion is 5.0.
❑ Platform is Windows.
❑ Security is U.
❑ OS-or-CPU is Windows NT 5.1
❑ Localization information is en-US.
❑ PrereleaseVersion is rv:0.9.4.
❑ GeckoVersion is 20011128.
❑ ApplicationProduct is Netscape 6
❑ ApplicationProductVersion is 6.2.1.

 

The following table displays some common browsers and their user-agent strings

Browser	User-Agent String
Internet Explorer 6.0	Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1) (Windows XP)
Mozilla 1.5	Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.5) (Windows XP) Gecko/20031007
Firefox 0.92	Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7) (Windows XP) Gecko/20040707 Firefox/0.8
Opera 7.54	Opera/7.54 (Windows NT 5.1; U) (Windows XP)
Safari 1.25	Mozilla/5.0 (Macintosh; U; PPC Mac OS X; en) (MacOS X) Apple-WebKit/124 (KHTML, like Gecko) Safari/125.1