Marc Andreessen
Marc Lowell Andreessen (born July 9, 1971) co-authored the NCSA Mosaic web browser in 1993, co-founded Netscape Communications in 1994, and co-founded the venture capital firm Andreessen Horowitz in 2009.1 His firm has backed companies including Facebook, GitHub, Airbnb, Lyft, Coinbase, and Slack, and managed over $35 billion in assets as of the mid-2020s.7
Early Life
Andreessen was born in Cedar Falls, Iowa, and raised in New Lisbon, Wisconsin, which he later described as "the sticks."1 His father, Lowell Andreessen, worked as a sales manager for the seed company Pioneer Hi-Bred International; his mother, Patricia, worked in customer service at Lands' End.1 He discovered programming at age 12.1
He enrolled at the University of Illinois at Urbana-Champaign and earned a BS in computer science in December 1993.1 While an undergraduate, he held two internships at IBM in Austin, Texas, working on AIX graphics software.1 He also worked as a part-time programmer at the National Center for Supercomputing Applications (NCSA) for $6.85 per hour.1
Career
NCSA Mosaic (1992–1993)
At NCSA, Andreessen became familiar with Tim Berners-Lee's early World Wide Web standards.1 After seeing the graphical browser ViolaWWW in late 1992, he and full-time NCSA employee Eric Bina built a browser with integrated graphics capable of running on Windows, Mac, and Unix systems.1 They released Mosaic in 1993. The browser contributed to a 342,000 percent increase in web traffic within a year; the number of websites grew from 50 to 10,000, and the share of internet users browsing the web rose from 1% to 25%.1 NCSA declined to credit Andreessen and Bina for their contribution, and Andreessen left the center in 1994.1
Netscape (1994–1998)
After graduating, Andreessen moved to California to work briefly at Enterprise Integration Technologies.1 Jim Clark, the founder of Silicon Graphics who had recently left that company, approached Andreessen with a proposal to commercialize the Mosaic concept. The two co-founded Mosaic Communications Corporation in Mountain View, California, with Andreessen as co-founder and vice president of technology.1 The University of Illinois objected to the Mosaic name, so the company renamed itself Netscape Communications, and its flagship product became Netscape Navigator.1
Netscape's IPO on August 9, 1995, opened at $28 per share and closed at $58.25 — one of the largest first-day gains in IPO history at the time. Andreessen appeared on the cover of Time magazine that year.1 AOL acquired Netscape in 1999 for $4.3 billion.1
Loudcloud and Opsware (1999–2007)
After the AOL acquisition, Andreessen co-founded Loudcloud with Ben Horowitz, Tim Howes, and In Sik Rhee in 1999.1 The company provided cloud hosting and software services to internet businesses. Loudcloud went public in March 2001, raising $162.5 million — one of the few tech IPOs completed during the dot-com bust.1 In 2003, the company sold its hosting business to Electronic Data Systems (EDS) and renamed itself Opsware, shifting focus to data center automation software, with Andreessen serving as chairman.1 Hewlett-Packard acquired Opsware in 2007 for $1.6 billion in cash, or $14.25 per share.5 Andreessen received approximately $138 million from the transaction.8
Andreessen Horowitz (2009–present)
Between 2005 and 2009, Andreessen and Horowitz separately invested a combined $80 million in 45 startups, including Twitter.1 On July 6, 2009, they announced Andreessen Horowitz with an initial fund of $300 million.1 Within three years, the firm grew to $2.7 billion under management across three funds.1 By 2024, the firm raised $7.2 billion in a single fundraise.7 Notable exits that shaped the firm's reputation include Okta, PagerDuty, Slack, Lyft, DigitalOcean, and Coinbase.1
In 2021, the firm launched a $2.2 billion crypto-focused fund, followed by a $4.5 billion crypto and blockchain fund in 2022.1 In 2023, the firm established the American Dynamism fund targeting hard tech sectors including defense, space, manufacturing, and robotics.1 In January 2025, the firm closed its London office — its first European location — and refocused on the U.S. crypto market.1
Investment Philosophy
Andreessen outlined his thesis in the August 2011 Wall Street Journal op-ed "Why Software Is Eating the World," arguing that software companies were disrupting and displacing established businesses in industries from retail to entertainment to financial services.6 The essay became one of the most-cited documents in Silicon Valley. At a16z, the firm built an unusually large support staff — including marketing, recruiting, executive, and technical specialists — to provide portfolio companies with services beyond capital.7
Andreessen has described his firm's approach as a "full-stack" model for venture capital, in which the firm acts as a platform rather than only a capital provider.7 He is a proponent of Bitcoin and cryptocurrency broadly, and the firm has made crypto and blockchain investing a central vertical.1
Notable Investments
| Company | Sector | Outcome |
|---|---|---|
| Social | Board member; major early-stage investor | |
| GitHub | Developer tools | Acquired by Microsoft for $7.5B (2018) |
| Airbnb | Travel | IPO 2020 |
| Lyft | Rideshare | IPO 2019 |
| Coinbase | Crypto exchange | IPO 2021 |
| Slack | Enterprise software | Acquired by Salesforce for $27.7B (2021) |
| Skype | Communications | Sold stake to Microsoft for $8.5B (2011) |
| Social | Early angel investment |
Andreessen joined the board of eBay in 2008 and resigned in 2014 over a dispute with investor Carl Icahn regarding the PayPal spinoff.1 He has served on the board of Meta Platforms since its early days as a board member and continues in that role.1 In 2026, he was appointed to the President's Council of Advisors on Science and Technology by President Donald Trump.1