Differentiate IE7 browser and browser in IE7 compatibility mode

For at least IE8 and IE9, you can check whether navigator.userAgent has the substring Trident in it. An IE8+ always has a Trident in its user-agent, where an IE7 doesn’t. See this answer and the MSDN link in it.

IE10 seems trickier: it is reported in the comments below that Trident is not always present with IE7 emulation mode. Probably the OS string (eg. Windows NT 6.2) will still reveal IE10, if IE10 will not be available on any platform where IE7 is available.

Please also note that the HTTP User-Agent header might not always match navigator.userAgent. This is the case at least with IE9 that has compatiblity mode on (sends an IE7 User-Agent header) but detects something like IE=Edge in the response (navigator.userAgent turns back to IE9).

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