Why is IE9 sending a user agent string of IE6?

Question

I'm getting a bunch of errors on my application with the user agent string being:

 Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1) 

Looking this up on useragentstring.com, this is supposed to be internet explorer 6 while the user claims he is using internet explorer 9.

I'm no expert in user agents, can someone tell me why IE9 would be disguising as IE6, or what else am I missing here? Is there a way to "really" detect the browser server-side? Can I do a redirect server-side (using Coldfusion) or in htaccess?

Thanks!

Answer 1

This is what I could find from an archive of almost all user agent strings.

Explanation: This string has bit of history. We originally published it as a EudoraWeb string - since it was self identified by a site user as being that. However:

We got some email about this string suggesting that it was not eudora since it had no Eudora in it. To be fair the supplier of the string also voiced some doubt since it was left to the user to identify the string. If anyone can shed some more light on this topic - please email us and we'll publish.

We got some more comment which says it looks so much like a normal Win 2K that we've moved it. The suggestion is that both .NET strings are added when the MS WindowsUpdate system is used. Explanation from Matt Hair - thanks.

Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1)

http://www.zytrax.com/tech/web/msie-history.html