Why does Internet Explorer (9) report "Mozilla" in UserAgent?

Question

Why does Internet Explorer has Mozilla in UserAgent?

In Firefox it's stating:

Mozilla/5.0 (Windows NT 6.1; rv:7.0.1) Gecko/20100101 Firefox/7.0.1

In Interner Explorer it's stating:

Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Trident/5.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; Tablet PC 2.0; .NET4.0E; .NET4.0C)

In some blogs/forums it's mentioned, that it is due to some historical reasons, but what's the reason?

It would be very helpful to know about it.

Answer 1

this should do it:

http://en.wikipedia.org/wiki/Mozilla

When users visit a website (via a user agent such as a web browser), a text string is generally sent to identify the user agent to the web server. It is known as the "user agent string". The Netscape web browser identified itself as "Mozilla/" followed by some information about the operating system it was running on.

Because the Netscape browser initially implemented many features not available in other browsers and quickly came to dominate the market, a number of web sites were designed to work, or work fully, only when they detected an appropriate version of Mozilla in the user agent string. Thus, competing browsers began to emulate ("cloak" or "spoof") this string in order to also work with those sites. The earliest example of this is Internet Explorer's use of a user agent string beginning "Mozilla/ (compatible; MSIE ...", in order to receive content intended for Netscape, its main rival at the time of its development. This format of user agent string has since been copied by other user agents, and persisted even after Internet Explorer came to dominate the browser market.

wiki knows everything

also https://superuser.com/questions/113020/why-does-internet-explorer-calls-itself-mozilla