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The earliest example of this is Internet Explorer's use of a User-Agent string beginning "Mozilla/<version> (compatible; MSIE <version>...", in order to receive content intended for Netscape Navigator, its main rival at the time of its development. This was not a reference to the open-source Mozilla browser, which was developed much later, but to the original codename for Navigator, which was also the name of the Netscape company mascot. This format of User-Agent string has since been copied by other user agents, partly because Explorer, in turn, came to dominate.
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