Marc Andreessen Bio
Marc Lowell Andreessen (born 9 July 1971) is an American businessman, venture capitalist, and former software engineer. He is best known as the co-author of Mosaic, the web browser that helped popularize the World Wide Web in 1993, and as the co-founder of Netscape Communications, one of the first commercial internet software companies. Andreessen later co-founded the cloud-services firm Opsware and, with Ben Horowitz, launched the Silicon Valley venture capital firm Andreessen Horowitz in 2009.
Through Andreessen Horowitz, he has invested in many of the most influential technology companies of the modern era, including Facebook, GitHub, Twitter, and Pinterest. Public estimates put his personal net worth in the billions as of the mid-2020s, reflecting both his long career in software and his central role in the venture capital industry.
Early Life and Background
Marc Lowell Andreessen was born on 9 July 1971 in Cedar Falls, Iowa, and raised in the small community of New Lisbon, Wisconsin, a place he has described as “the sticks.” He is the son of Lowell Andreessen, a sales manager for the seed producer Pioneer Hi-Bred International, and Patricia Andreessen, who worked in customer service at Lands’ End. Andreessen also has a younger brother named Jeff, though Andreessen has noted in interviews that his relationships with his immediate family were strained and that he prefers not to discuss them.
Andreessen discovered computer programming at the age of 12, an interest that shaped the rest of his education and early career. He attended New Lisbon High School in Wisconsin and went on to study computer science at the University of Illinois at Urbana–Champaign, where he also worked as a programmer at the National Center for Supercomputing Applications (NCSA). At NCSA he became familiar with Tim Berners-Lee’s open standards for the World Wide Web and, with colleague Eric Bina, began developing a graphical browser that could run on Windows and Macintosh computers.
Path to Venture Capital
In December 1993, Andreessen earned his bachelor’s degree in computer science from the University of Illinois at Urbana–Champaign. By that point he had already helped release the Mosaic web browser in 1993, which caused web traffic to surge by more than 300,000 percent in a single year and pushed the number of websites on the internet from roughly 50 to about 10,000. Frustrated that NCSA did not credit the Mosaic team, Andreessen decided to leave the center in 1994.
Shortly after graduating, he moved to California, where he met Silicon Graphics founder Jim Clark. Together they co-founded Mosaic Communications Corporation in Mountain View, California, which was renamed Netscape Communications after the University of Illinois objected to the original name. That company became the foundation of Andreessen’s career in business, and a subsequent sale to AOL gave him the capital and profile to launch later ventures, including the venture capital firm Andreessen Horowitz.
Marc Andreessen Career
Early Career (1993–1998)
Andreessen’s professional career began in earnest with the 1993 release of the NCSA Mosaic web browser, the first widely used graphical browser for both Windows and Macintosh. The success of Mosaic caught the attention of Jim Clark, and the two co-founded Mosaic Communications Corporation, soon renamed Netscape Communications, with Andreessen serving as co-founder and vice president of technology. The company launched the Netscape Navigator browser, which became the first successful commercial web browser offered at no cost to users.
Netscape’s initial public offering in 1995 placed Andreessen on the cover of Time and other major publications, making him one of the most recognized young figures in the technology industry. The company was later acquired in 1999 by AOL for $4.3 billion, and Andreessen joined AOL as chief technical officer once the acquisition closed.
Netscape Era (1994–1999)
Under Andreessen’s leadership as co-founder and vice president of technology, Netscape Communications grew rapidly in Mountain View, California. The company offered a wide range of products, including clients, servers, development tools, and e-commerce applications, and it simplified the browsing experience while adding speed and built-in support for financial transactions. Netscape Navigator quickly became the dominant browser of the mid-1990s.
The 1995 Netscape IPO was one of the defining moments of the dot-com era and turned Andreessen into a public figure almost overnight. He appeared on the cover of Time and was profiled in numerous business publications. After the 1999 acquisition by AOL, Andreessen was named chief technical officer, and the same year he was recognized on the MIT Technology Review TR100 list as one of the top 100 innovators in the world under the age of 35.
Opsware and Ning Era (1999–2009)
After leaving AOL, Andreessen co-founded Loudcloud with Ben Horowitz, Tim Howes, and In Sik Rhee. Originally focused on internet hosting and software services, Loudcloud sold its hosting business to EDS and rebranded as Opsware in 2003. Andreessen served as chairman of the company, which was acquired by Hewlett-Packard in 2007 for $1.6 billion, an early example of a software-as-a-service and cloud-hosting company achieving a major exit.
Andreessen also co-founded and chaired Ning, a platform that allowed users to build social networking websites. In September 2011, Ning was sold to Mode Media for a reported $150 million, after which Andreessen joined the board of Glam Media. Between 2005 and 2009, he and Ben Horowitz also made a combined $80 million in personal investments across 45 startups, including early bets on Twitter and Qik, building their reputations as “super angel” investors.
Andreessen Horowitz Era (2009–Present)
On July 6, 2009, Andreessen and Horowitz formally launched Andreessen Horowitz, a Silicon Valley venture capital firm that began with an initial capitalization of $300 million. Within three years the firm grew to $2.7 billion under management across three funds, and by the early 2020s it had backed successful IPOs including Okta, PagerDuty, Pinterest, Accolade, Slack, Lyft, DigitalOcean, and Coinbase. In 2021 the firm launched a $2.2 billion crypto-focused fund, followed by a $4.5 billion crypto and blockchain fund in 2022.
Andreessen Horowitz has also expanded into newer themes, launching the American Dynamism fund in 2023 to back defense, manufacturing, space, and robotics startups, and in July 2025 led the largest seed round in history, a $2 billion investment in the AI startup Thinking Machines Lab. Andreessen serves on the boards of Meta and other technology companies, advises founders whose firms the firm has funded, and remains one of the most active venture capitalists in the United States.
Notable Events and Milestones
Among Andreessen’s signature achievements is his role in the 1993 launch of Mosaic, the browser that helped move the World Wide Web from a research curiosity into a mainstream tool. He co-founded Netscape, led it through a landmark IPO in 1995, and oversaw its sale to AOL in 1999 for $4.3 billion. He later co-founded Andreessen Horowitz, which has become one of the most influential venture capital firms of the 21st century, and in 2012 he was named to the Time 100 list of the most influential people in the world.
Marc Andreessen Career Wins
Across more than three decades in technology and venture capital, Marc Andreessen has built a record of high-profile exits and influential investments. He co-created the Mosaic browser, co-founded Netscape and Opsware, and launched Andreessen Horowitz, each of which produced major outcomes in their respective industries.
Career Highlights
Andreessen’s earliest major win was the release of Mosaic in 1993, which helped transform the World Wide Web into a mass medium. He followed that with the co-founding of Netscape Communications, the company behind the Netscape Navigator browser and one of the most successful IPOs of the 1990s. More recently, his firm Andreessen Horowitz has produced IPOs including Pinterest, Lyft, Coinbase, Slack, Okta, PagerDuty, DigitalOcean, and Accolade.
Andreessen has also generated notable returns from personal investments, including early positions in LinkedIn, Facebook, GitHub, and Twitter, and from a 2009 investor group that took a majority stake in Skype at a $2.75 billion valuation, only to see Microsoft acquire Skype in 2011 for $8.5 billion.
Other Wins & Achievements
Andreessen has been recognized on several influential industry lists, including the Time 100 in 2012, the MIT Technology Review TR100 in 1999, and the Forbes Midas List of top tech investors. He was also one of the inaugural laureates of the Queen Elizabeth Prize for Engineering in 2013 and an early inductee of the World Wide Web Hall of Fame in 1994.
Marc Andreessen Family
Family Background and Lineage
Marc Lowell Andreessen was born to Lowell Andreessen, who worked as a sales manager for the seed producer Pioneer Hi-Bred International, and Patricia Andreessen, who worked in customer service for Lands’ End. He has a younger brother, Jeff, who was studying history at the University of Wisconsin in the late 1990s. Andreessen has described himself as German-American and has noted in interviews that his relationships with his immediate family were difficult during his formative years.
Personal Life
Andreessen married Laura Arrillaga in 2006, after the couple met at a New Year’s Eve dinner he organized in 2005. Laura Arrillaga is the founder of the Silicon Valley Social Venture Fund and the daughter of Silicon Valley real estate developer John Arrillaga. The couple has one son, also named John, who was carried by a gestational surrogate. Andreessen and his wife reside in Atherton, California, and made headlines in 2021 when they purchased a Malibu property for $177 million, at the time the highest price paid for a residential property in California.