Andreessen, Marc (1972– )

US systems developer and co-author of the first widely available graphical browser for the World Wide Web, Mosaic.

Andreessen wrote Mosaic with fellow researcher Eric Bina while working at the National Center for Supercomputing Applications (NCSA), based at the University of Illinois. In 1994 both moved to the start-up company Netscape Communications Corporation to work on the next generation of browser software. This included Netscape Navigator, which was made freely available on the Internet and contributed to the explosive growth of the World Wide Web in the mid-1990s.

Andressen became chief technology officer at America Online, when it bought Netscape in March 1999. Six months later, however, he left to found Web hosting company Loudcloud, of which he is chairman. Loudcloud changed its name to Opsware in 2003 and the company was purchased by Hewlett-Packard in 2007. Andreessen is now focusing on new ventures in social networking.