Common User Agent Strings

A list of user agents, and where they come from (i.e. which browser or search engine output them)
User Agent Source
Mozilla/5.0 (Windows; U; Windows NT 5.1; en-GB; rv:1.8.1.6) Gecko/20070725 Firefox/2.0.0.6 Firefox 2.0, Windows XP
Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1) Internet Explorer 7, Windows Vista
Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; .NET CLR 1.1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.04506.30) Internet Explorer 7, Windows XP
Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; .NET CLR 1.1.4322) Internet Explorer 6, Windows XP
Mozilla/4.0 (compatible; MSIE 5.0; Windows NT 5.1; .NET CLR 1.1.4322)
Internet Explorer 5, Windows XP
Opera/9.20 (Windows NT 6.0; U; en) Opera 9.2, Windows Vista
Opera/9.00 (Windows NT 5.1; U; en) Opera 9.0, Windows XP
Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; en) Opera 8.50 Opera 8.5, Windows XP
Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; en) Opera 8.0 Opera 8.0, Windows XP
Mozilla/4.0 (compatible; MSIE 6.0; MSIE 5.5; Windows NT 5.1) Opera 7.02 [en] Opera 7.02, Windows XP
Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.5) Gecko/20060127 Netscape/8.1 Netscape 8.1, Windows XP
Googlebot/2.1 ( http://www.googlebot.com/bot.html)  Googlebot 2.1 (search engine bot)
Googlebot-Image/1.0 ( http://www.googlebot.com/bot.html)  Googlebot Image 1.0 (search engine image bot)
Mozilla/2.0 (compatible; Ask Jeeves)  Ask Jeeves (search engine bot)
msnbot-Products/1.0 (+http://search.msn.com/msnbot.htm)  Windows Live (search engine bot)