Making Firefox pretend to be IE (user agent spoofing)

This content is 18 years old. I don't routinely update old blog posts as they are only intended to represent a view at a particular point in time. Please be warned that the information here may be out of date.

Our corporate intranet doesn’t always play nicely with browsers that it doesn’t recognise. I’ve previously written about making Internet Explorer (IE) 7.0 pretend to be IE 6.0 but today I needed to change the behaviour of Firefox 1.5 to trick the intranet into thinking I’m using IE (I have IE installed, but as its not my default browser, clicking a link in an e-mail, for example, opens in Firefox), thus avoiding messages like the following:

Browser requirements
Internet Explorer 4 (or later) is required
Your current browser, Default 0.0, does not support the features and security requirements of this site

Thankfully, John Bokma’s article on changing the user agent in Firefox answered that question for me and after I’d entered a new general.useragent.override string in my about:config page everything jumped into life. For reference, my original (Firefox) user agent string was:

Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8) Gecko/20051111 Firefox/1.5
and the override (mimicking my Internet Explorer configuration) is:

Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; .NET CLR 1.1.4322; InfoPath.1)

If you want to check your string, there’s a history (including why Microsoft Internet Explorer user agent strings pretend to be Mozilla) and detection script on Dan Tobias’ Web Tips site. Further information (including common user agent strings) can also be found on Wikipedia.

On a slightly different note, whilst I was researching this, I stumbled across an article on how to make Firefox look like Internet Explorer (i.e. visually, not programmatically).

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