Marc Andreessen

In February 1994 Jim Clark invited about a dozen people to dinner at Il Fornaio in Palo Alto and pitched them on founding a new company. Marc Andreessen, who had co-written the Mosaic browser as a part-time university employee earning $6.85 an hour, was the only one who said yes. What he took from Clark was a working principle he has repeated since: the world is more malleable than it looks.¹

Andreessen is the co-creator of Mosaic, the first widely used graphical web browser, the co-founder of Netscape, the company that turned that browser into a commercial product and made the internet usable by ordinary people, and the co-founder and general partner of Andreessen Horowitz (a16z), one of the largest venture capital firms in the world. Three decades after that dinner he helps direct a firm managing tens of billions of dollars across software, biotech, and artificial intelligence.

Background

Andreessen was born on July 9, 1971, in Cedar Falls, Iowa, and raised in New Lisbon, Wisconsin, a small town he has described as having one stoplight and a party-line telephone. His father, Lowell, was a sales manager for the seed company Pioneer Hi-Bred International; his mother, Patricia, worked in customer service for the mail-order retailer Lands' End. He began programming around age 12. He studied computer science at the University of Illinois at Urbana-Champaign, interned twice at IBM in Austin, Texas, on graphics software, and received his bachelor's degree in December 1993.

Getting started

While still a student, Andreessen took a part-time programming job at the University of Illinois's National Center for Supercomputing Applications (NCSA), earning $6.85 an hour. There he teamed with programmer Eric Bina to build Mosaic, a browser that displayed inline images alongside text and let users click directly on hyperlinks, both novel at the time. The two wrote roughly 9,000 lines of code in about six weeks; Mosaic shipped in 1993 and is widely credited with driving a dramatic surge in internet traffic within a year of its release. When a New York Times feature on the browser credited NCSA but did not name Andreessen or Bina, Andreessen left the university's orbit for Silicon Valley.¹

Clark had founded Silicon Graphics and left it after conflict with the managers who succeeded him. The two founded Mosaic Communications Corporation that April, soon renamed Netscape Communications, and hired much of the original NCSA Mosaic team to rebuild the browser from scratch, avoiding intellectual-property disputes with the university.

What he built

Netscape Navigator launched in late 1994 and quickly became the dominant way people accessed the web. The company went public on August 9, 1995, at $28 a share, closing its first day at $58.25 and valuing the company at roughly $3 billion, with Andreessen's own stake near $59 million. The Netscape IPO is widely regarded as the opening event of the dot-com boom. Netscape later added Jim Barksdale, a veteran telecom executive, as CEO to run operations alongside the 24-year-old Andreessen, a pairing Andreessen has since cited as a model for combining an experienced operator with a founder's vision rather than replacing the founder outright.¹ Netscape's browser share fell through the late 1990s as Microsoft bundled Internet Explorer with Windows, and in 1999 AOL acquired Netscape in a stock deal valued at about $10 billion.

After Netscape, Andreessen co-founded the infrastructure software company Loudcloud in 1999, restructured as Opsware after it sold its managed-hosting business, and acquired by Hewlett-Packard in 2007. He also co-founded the social-networking platform Ning in 2004. In 2009, he and Ben Horowitz, his Netscape and Opsware colleague, founded the venture capital firm Andreessen Horowitz with an initial fund of $300 million. The firm grew into one of the largest venture investors in the world, backing companies including Facebook, Airbnb, Coinbase, GitHub, Skype, and Stripe, and, in the 2020s, a wide set of artificial intelligence companies. By early 2026 the firm's assets under management had grown to more than $90 billion.

How he operates

Andreessen describes his own working style as "zero introspection: as little as possible, move forward, go," and cites the retailer Sam Walton as an example of the same forward-acting type.¹ He says he built a16z's founding investment thesis around a barbell structure he observed in other knowledge-work industries, such as talent agencies and private equity, where boutiques and large scaled platforms both thrive while the middle tier declines; a16z was built to be the scaled platform in venture capital, offering founders services beyond capital, including recruiting, PR, and regulatory support. He argues founders, not professional managers, should retain control of the companies they start, pointing to Jim Clark's own experience at Silicon Graphics, where he says correct predictions about cheap graphics chips and networked computers were blocked by the professional manager who replaced him.¹ Andreessen has also written extensively about how the internet reshapes media and politics, applying Marshall McLuhan's idea that the internet's native content form is the viral meme and moral panic rather than television's morality play.²

Where things stand

As of the mid-2020s, Andreessen remains a general partner at Andreessen Horowitz alongside Ben Horowitz, overseeing a firm that has grown from its 2009 founding fund into a multi-strategy manager spanning venture, growth, biotech, American dynamism, and crypto investing, with assets under management exceeding $90 billion. He has become an outspoken commentator on technology, media, and politics, publishing essays such as "The Techno-Optimist Manifesto" and hosting long-form interviews through a16z's media arm.² He advised Donald Trump's political operation in 2024. Forbes has estimated his net worth in the range of roughly $1.9 billion as of 2026.

Key facts

• Co-built the Mosaic browser in about six weeks at NCSA in 1992 to 1993, working part-time for $6.85 an hour alongside Eric Bina.
• Was the only person, out of about a dozen invited, to accept Jim Clark's dinner pitch to found a new company in February 1994, leading directly to Netscape.
• Netscape's August 1995 IPO closed with the company valued at roughly $3 billion and Andreessen's own stake near $59 million; AOL acquired Netscape in 1999 for about $10 billion.
• Co-founded Andreessen Horowitz with Ben Horowitz in 2009 with a $300 million debut fund; the firm's assets under management surpassed $90 billion by early 2026.
• Describes his operating principle as "zero introspection, move forward, go," and has proposed a "MilliElon" scale for measuring founder intensity against Elon Musk as a reference point.