Internet Explorer 11 is pretending it’s Firefox
Microsoft has figured out how to get websites to stop treating Internet Explorer like a second-class web browser: it’s going to disguise itself as Firefox.
What Looks Like IE11 but Smells Like Firefox?
The user-agent string for Internet Explorer 11 is shorter than previous versions and has some interesting changes:
Mozilla/5.0 (Windows NT 6.3; Trident/7.0; rv 11.0) like Gecko
Compare this to the Internet Explorer 10 user-agent string (on Windows 7):
Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.1; WOW64; Trident/6.0)
The biggest change in IE11 is the removal of ‘MSIE’. I suspect that has been done for one reason: to prevent sites serving invalid IE6/7/8 code to modern editions of the browser. Recent releases of IE’s Trident engine are closer to Gecko or WebKit than legacy editions of itself. By removing the ‘MSIE’ string, Microsoft is breaking detection code and making many sites work as they should.
The point is: none of this matters. If you’re browser sniffing, probably you are almost certainly doing something wrong! While it seems an obvious solution, browser sniffing is a fragile technique that introduces more maintenance headaches than it prevents.