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Lore & Background

Andreessen was born in Cedar Falls, Iowa, and raised in New Lisbon, Wisconsin, which he considered 'the sticks.' He is the son of Patricia, a customer service operator at Lands' End, and Lowell Andreessen, a sales manager for Pioneer Hi-Bred International. He has a younger brother named Jeff. Andreessen has stated that he had problematic relationships with his parents and brother, and that he did not like to talk about them. He discovered programming at age 12. In December 1993, he received his bachelor's degree in computer science from the University of Illinois at Urbana–Champaign (UIUC). As an undergraduate, he interned twice at IBM in Austin, Texas, working in the AIX graphics software development group. He also worked as a programmer, earning $6.85 per hour (equivalent of $15.49/hr in 2026), at the National Center for Supercomputing Applications (NCSA). After being shown the graphic web browser ViolaWWW in late 1992, Andreessen and full-time salaried co-worker Eric Bina worked on creating a browser with integrated graphics that could be ported to a wide range of computers, including Windows. The result was the Mosaic web browser released in 1993, which led to a 342,000 percent increase in web traffic in a year. Before Mosaic, there had only been 50 websites on the Web; the number now increased to 10,000, while the percentage of internet users who surfed the Web increased from 1% to 25%. The NCSA refused to give the Mosaic team credit for their contribution, so Andreessen, disillusioned, decided to leave the center in 1994.

Reader's Guide

After graduating in 1993, Andreessen moved to California to work at Enterprise Integration Technologies. He then met Jim Clark, founder of Silicon Graphics, who believed the Mosaic browser had great commercial possibilities. Soon, Mosaic Communications Corporation was in business in Mountain View, California, with Andreessen as co-founder and vice president of technology. The University of Illinois was unhappy with the company's use of the Mosaic name, so it changed its name to Netscape Communications, and its flagship browser was named Netscape Navigator. Netscape was the first successful commercial web browser (offered for free). Netscape's IPO in 1995 put Andreessen in the public eye. He was on the cover of Time and other publications. Netscape was acquired in 1999 for $4.3 billion by AOL. Andreessen's hiring as its chief technical officer was contingent on the completion of the acquisition. The same year, he was named to the MIT Technology Review TR100 as one of the top 100 innovators in the world under the age of 35. After AOL acquired Netscape, Andreessen founded Opsware with Ben Horowitz, Tim Howes, and In Sik Rhee. Originally named Loudcloud, the company provided computing, hosting and software services. Loudcloud sold its hosting business to EDS and changed its name to Opsware in 2003, with Andreessen serving as chairman. It was acquired by Hewlett-Packard for $1.6 billion in 2007. On July 6, 2009, Andreessen and Horowitz announced their venture-capital firm Andreessen Horowitz, beginning with an initial capitalization of $300 million. Within three years the firm grew to $2.7 billion under management across three funds. In 2012, its portfolio included Facebook, Foursquare, GitHub, Pinterest, Twitter and Honor Technology. In 2021, Business Insider noted successful IPOs including Okta, Inc., PagerDuty, Pinterest, Accolade, Slack Technologies, Lyft, DigitalOcean and Coinbase. Both Andreessen and the firm have an interest in cryptocurrency. In 2021, the firm launched a $2.2 billion crypto-focused fund, followed by a 2022 $4.5 billion fund dedicated to crypto and blockchain. In 2023, the firm launched the American Dynamism fund, focusing on hard tech sectors serving national interest, including space, defense, manufacturing, robotics. In 2024, Andreessen Horowitz launched the 12-month American Dynamism Engineering Fellows Program. On September 1, 2009, an investor group including Andreessen Horowitz acquired a majority stake in Skype at a valuation of $2.75 billion. The deal paid off in May 2011 when Microsoft bought Skype for $8.5 billion. Andreessen joined the eBay board of directors in 2008 and served for six years. In October 2014, he resigned due to the company's decision to break off PayPal. In July 2025, Andreessen Horowitz led the largest seed round in history for AI startup Thinking Machines Lab, raising a record $2 billion, valuing the firm at $12 billion. Andreessen cofounded and chaired Ning, the third company he established, after Netscape and Loudcloud. In September 2011, Ning was sold to Mode Media for a reported price of $150 million.

Did You Know?

• Andreessen discovered programming at age 12.
• He earned $6.85 per hour (equivalent of $15.49/hr in 2026) as a programmer at NCSA.
• Mosaic led to a 342,000 percent increase in web traffic in a year.
• Before Mosaic, there were only 50 websites on the Web; after, the number increased to 10,000.
• In July 2025, Andreessen Horowitz led the largest seed round in history for AI startup Thinking Machines Lab, raising $2 billion.