Marc Andreessen
Co-author of Mosaic, co-founder of Netscape, co-founder of Andreessen Horowitz.
via Wikipedia: Marc Andreessen · see source
Marc Lowell Andreessen was born on July 9, 1971, in Cedar Falls, Iowa, and grew up in New Lisbon, Wisconsin—a place he described as “the sticks.” His father, Lowell, was a sales manager for seed producer Pioneer Hi-Bred International, and his mother, Patricia, worked as a customer service operator at Lands’ End. He has a younger brother named Jeff, but Andreessen has said he had difficult relationships with his parents and brother and preferred not to discuss them.
He started programming at age 12. As an undergraduate at the University of Illinois at Urbana–Champaign, he interned twice at IBM in Austin, Texas, working on AIX graphics software. He also worked as a programmer at the National Center for Supercomputing Applications (NCSA), earning $6.85 an hour. There, he learned about Tim Berners-Lee’s open web standards but found the existing browser too complex for general use. After seeing the ViolaWWW browser in late 1992, Andreessen and co-worker Eric Bina built a new browser with integrated graphics that could run on multiple systems, including Windows. The result was Mosaic, released in 1993. It caused web traffic to surge by 342,000 percent in a year, boosted the number of websites from 50 to 10,000, and increased the share of internet users browsing the web from 1 percent to 25 percent. Mosaic is often called the first successful web browser and was the first widely used on both Windows and Mac. The NCSA refused to credit the Mosaic team, so Andreessen left in 1994.
After graduating in 1993, he moved to California to work at Enterprise Integration Technologies. He then met Jim Clark, former founder of Silicon Graphics, who saw commercial potential in Mosaic. They started Mosaic Communications Corporation in Mountain View, California, with Andreessen as co-founder and vice president of technology. The University of Illinois objected to the name, so the company became Netscape Communications, and its browser was renamed Netscape Navigator. It was the first successful commercial web browser, offered for free, with a simpler interface, faster performance, and tools for financial transactions. Netscape’s 1995 IPO made Andreessen a public figure, landing him on the cover of Time and other magazines. AOL acquired Netscape in 1999 for $4.3 billion, and Andreessen became its chief technical officer as part of the deal. That same year, MIT Technology Review named him one of the top 100 innovators under 35.
After the acquisition, Andreessen co-founded Opsware (originally called Loudcloud) with Ben Horowitz, Tim Howes, and In Sik Rhee. The company provided computing, hosting, and software services for internet and e-commerce firms. Loudcloud sold its hosting business to EDS and renamed itself Opsware in 2003, with Andreessen as chairman. Hewlett-Packard bought Opsware for $1.6 billion in 2007. It was among the first companies to offer software as a service and attempt cloud hosting.
Between 2005 and 2009, Andreessen and Horowitz individually invested $80 million in 45 startups, including Twitter and Qik, gaining reputations as super angel investors. On July 6, 2009, they announced their venture-capital firm Andreessen Horowitz, starting with $300 million. Within three years, it grew to $2.7 billion across three funds. By 2012, its portfolio included Facebook, Foursquare, GitHub, Pinterest, Twitter, and Honor Technology. Successful IPOs that boosted the firm’s reputation include Okta, PagerDuty, Pinterest, Accolade, Slack Technologies, Lyft, DigitalOcean, and Coinbase. Andreessen and the firm have focused on cryptocurrency, launching a $2.2 billion crypto fund in 2021 and a $4.5 billion crypto and blockchain fund in 2022. Portfolio companies in crypto and NFTs include Alchemy, Dapper Labs, Avalanche, OpenSea, Solana, and Yuga Labs. In 2023, the firm launched the American Dynamism fund. Andreessen also co-founded Ning, a platform for social networking websites. In 2024, he became an advisor to Donald Trump. As of June 2026, Forbes estimated his net worth at $1.9 billion.
- field
- Business, venture capital, software engineering
- nationality
- American
- known_for
- Co-author of Mosaic, co-founder of Netscape, co-founder of Andreessen Horowitz
Verified Timeline
Lore & Background
Andreessen was born in Cedar Falls, Iowa, and raised in New Lisbon, Wisconsin, which he called '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. 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 at the National Center for Supercomputing Applications, earning $6.85 per hour (equivalent to $15.49/hr in 2026). 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. The new web browser led to a 342,000 percent increase in web traffic in a year. Before Mosaic, there had only been 50 websites on the Web; afterward, the number 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
Marc Andreessen's significance lies in his role as a pioneer of the graphical web browser, which transformed the Internet from a niche tool into a mass medium. Mosaic's inline images and cross-platform compatibility made the Web accessible to millions, and Netscape established the commercial web browser market. As a venture capitalist, Andreessen Horowitz has backed major companies including Facebook, Twitter, and Coinbase, and has been a leading investor in cryptocurrency and AI startups. His career reflects the evolution of the Internet from its early days to a central force in global commerce and culture.
Did You Know?
- Andreessen earned $6.85 per hour as a programmer at NCSA, equivalent to $15.49/hr in 2026.
- Mosaic led to a 342,000 percent increase in web traffic in a single year.
- Before Mosaic, there were only 50 websites on the Web; afterward, the number increased to 10,000.
- Andreessen was named to the MIT Technology Review TR100 as one of the top 100 innovators under age 35 in 1999.
- In July 2025, Andreessen Horowitz led the largest seed round in history for AI startup Thinking Machines Lab, raising $2 billion.
The Mosaic Breakthrough
Growing up in what he called 'the sticks' of New Lisbon, Wisconsin, a young Marc Andreessen stumbled into programming at just twelve years old. That early curiosity eventually led him to the National Center for Supercomputing Applications at the University of Illinois, where he earned a mere $6.85 an hour helping with computing work. Together with his full-time colleague Eric Bina, Andreessen set out to build a browser that could render inline images and run across multiple platforms, including Windows. Mosaic is widely credited as the first truly successful web browser and the first to be widely adopted on both Windows and Mac.
Netscape and the Dot-Com Era
There he caught the eye of Jim Clark, the man who had built Silicon Graphics and recently stepped away from it. Clark saw commercial potential in the Mosaic browser and proposed spinning it into a standalone internet software company. The venture launched in Mountain View under the name Mosaic Communications, with Andreessen serving as co-founder and vice president of technology. Legal pressure from the University of Illinois over the Mosaic name forced a rebrand: the company became Netscape Communications, and its flagship product was christened Netscape Navigator. Netscape offered a free commercial browser alongside servers, development tools, and e-commerce applications, all with a faster, more polished interface than its predecessor. That same year, MIT Technology Review named him to its TR100 list of the world's top hundred innovators under thirty-five.
Building Andreessen Horowitz
The growth was meteoric: within three years the firm managed $2.7 billion across three funds. Its portfolio by 2012 already included Facebook, Foursquare, GitHub, Pinterest, Twitter, and Honor Technology. Over the following years, successful IPOs from its portfolio—Okta, PagerDuty, Pinterest, Accolade, Slack, Lyft, DigitalOcean, and Coinbase—cemented the firm's standing in the industry.
From the Sticks to the Billionaire Class
He has a younger brother, Jeff, though Andreessen has spoken about problematic family relationships and has generally preferred not to discuss them. What began as a twelve-year-old tinkering with code in a Wisconsin bedroom eventually snowballed into one of the most consequential careers in technology. He interned twice at IBM in Austin, Texas, working on AIX graphics software and 3D language APIs, before taking a programmer role at the NCSA.
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Frequently Asked Questions
What is Marc Andreessen most famous for building?
He co-authored Mosaic, the first web browser capable of rendering images directly alongside text on a page. That project evolved into Netscape, which became the first commercially successful browser and put the web into mainstream hands.
What is Andreessen Horowitz and what role does Marc play in it?
Andreessen Horowitz is a venture capital firm he co-founded that invests in early-stage technology companies. As a principal, he helps guide funding decisions across software, hardware, and emerging tech sectors.
Why do fans of tech pioneers regard Marc Andreessen as a key figure?
He bridged the gap between academic web research and a product ordinary people could actually use, making the internet accessible to the general public. His later work as an investor continued that pattern by backing the next generation of digital tools.
What fields does Marc Andreessen span across his career?
His work touches software engineering, consumer technology, and venture capital. He started as a programmer building browsers and transitioned into a role shaping which startups receive the resources to grow.
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