Zuckerberg began using computers and writing software in middle school. His father taught him Atari BASIC Programming in the 1990s, and later hired software developer David Newman to tutor him privately. Zuckerberg took a graduate course in the subject at Mercy College near his home while still in high school. In one program, since his father's dental practice was operated from their home, he built a software program he called "ZuckNet" that allowed all the computers between the house and dental office to communicate with each other. It is considered a "primitive" version of AOL's Instant Messenger, which came out the following year.
According to writer Jose Antonio Vargas, "some kids played computer games. Mark created them." Zuckerberg himself recalls this period: "I had a bunch of friends who were artists. They'd come over, draw stuff, and I'd build a game out of it." However, notes Vargas, Zuckerberg was not a typical "geek-klutz", as he later became captain of his prep school fencing team and earned a classics diploma. Napster co-founder Sean Parker, a close friend, notes that Zuckerberg was "really into Greek odysseys and all that stuff", recalling how he once quoted lines from the Roman epic poem Aeneid, by Virgil, during a Facebook product conference.

During Zuckerberg's high school years, he worked under the company name Intelligent Media Group to build a music player called the Synapse Media Player. The device used machine learning to learn the user's listening habits, which was posted to Slashdot^[23] and received a rating of 3 out of 5 from PC Magazine.


College years

Vargas noted that by the time Zuckerberg began classes at Harvard, he had already achieved a "reputation as a programming prodigy". He studied psychology and computer science and belonged to Alpha Epsilon Pi and Kirkland House. In his sophomore year, he wrote a program that he called CourseMatch, which allowed users to make class selection decisions based on the choices of other students and also to help them form study groups. A short time later, he created a different program he initially called Facemash that let students select the best looking person from a choice of photos. According to Arie Hasit, Zuckerberg's roommate at the time, "he built the site for fun". Hasit explains:

We had books called Face Books, which included the names and pictures of everyone who lived in the student dorms. At first, he built a site and placed two pictures, or pictures of two males and two females. Visitors to the site had to choose who was "hotter" and according to the votes there would be a ranking.

The site went up over a weekend, but by Monday morning, the college shut it down, because its popularity had overwhelmed one of Harvard's network switches and prevented students from accessing the Internet. In addition, many students complained that their photos were being used without permission. Zuckerberg apologized publicly, and the student paper ran articles stating that his site was "completely improper.

Main articles: Facebook and History of Facebook

On February 4, 2004, Zuckerberg launched Facebook from his Harvard dormitory room. An earlier inspiration for Facebook may have come from Phillips Exeter Academy, the prep school from which Zuckerberg graduated in 2002. It published its own student directory, "The Photo Address Book", which students referred to as "The Facebook". Such photo directories were an important part of the student social experience at many private schools. With them, students were able to list attributes such as their class years, their friends, and their telephone numbers.

Once at college, Zuckerberg's Facebook started off as just a "Harvard thing" until Zuckerberg decided to spread it to other schools, enlisting the help of roommate Dustin Moskovitz. They began with Columbia University, New York University, Stanford, Dartmouth, Cornell, University of Pennsylvania, Brown, and Yale.   Samyr Laine, a triple jumper representing Haiti at the 2012 Summer Olympics, shared a room with Zuckerberg during Facebook's founding. "Mark was clearly on to great things," said Laine, who was Facebook's fourteenth user.

Zuckerberg, Moskovitz and some friends moved to Palo Alto, California in Silicon Valley where they leased a small house that served as an office. Over the summer, Zuckerberg met Peter Thiel, who invested in the company. They got their first office in mid-2004. According to Zuckerberg, the group planned to return to Harvard, but eventually decided to remain in California. They had already turned down offers by major corporations to buy the company. In an interview in 2007, Zuckerberg explained his reasoning: "It's not because of the amount of money. For me and my colleagues, the most important thing is that we create an open information flow for people. Having media corporations owned by conglomerates is just not an attractive idea to me.


He restated these goals to Wired magazine in 2010: "The thing I really care about is the mission, making the world open.  Earlier, in April 2009, Zuckerberg sought the advice of former Netscape CFO Peter Currie about financing strategies for Facebook.^[43] On July 21, 2010, Zuckerberg reported that the company reached the 500 million-user mark.  When asked whether Facebook could earn more income from advertising as a result of its phenomenal growth, he explained:

I guess we could ... If you look at how much of our page is taken up with ads compared to the average search query. The average for us is a little less than 10 percent of the pages and the average for search is about 20 percent taken up with ads ... That's the simplest thing we could do. But we aren't like that. We make enough money. Right, I mean, we are keeping things running; we are growing at the rate we want to.

In 2010, Steven Levy, who wrote the 1984 book Hackers: Heroes of the Computer Revolution, wrote that Zuckerberg "clearly thinks of himself as a hacker". Zuckerberg said that "it's OK to break things" "to make them better".^[45][46] Facebook instituted "hackathons" held every six to eight weeks where participants would have one night to conceive of and complete a project. The company provided music, food, and beer at the hackathons, and many Facebook staff members, including Zuckerberg, regularly attended. "The idea is that you can build something really good in a night", Zuckerberg told Levy. "And that's part of the personality of Facebook now ... It's definitely very core to my personality."


Wirehog

A month after Zuckerberg launched Facebook in February 2004, i2hub, another campus-only service, created by Wayne Chang, was launched. i2hub focused on peer-to-peer file sharing. At the time, both i2hub and Facebook were gaining the attention of the press and growing rapidly in users and publicity. In August 2004, Zuckerberg, Andrew McCollum, Adam D'Angelo, and Sean Parker launched a competing peer-to-peer file sharing service called Wirehog, a precursor to Facebook Platform applications.



Platform, Beacon, and Connect

On May 24, 2007, Zuckerberg announced Facebook Platform, a development platform for programmers to create social applications within Facebook. Within weeks, many applications had been built and some already had millions of users. It grew to more than 800,000 developers around the world building applications for Facebook Platform.

On November 6, 2007, Zuckerberg announced Beacon, a social advertising system that enabled people to share information with their Facebook friends based on their browsing activities on other sites. For example, eBay sellers could let friends know automatically what they have for sale via the Facebook news feed as they listed items for sale. The program came under scrutiny because of privacy concerns from groups and individual users. Zuckerberg and Facebook failed to respond to the concerns quickly, and on December 5, 2007, Zuckerberg wrote a blog post on Facebook, taking responsibility for the concerns about Beacon and offering an easier way for users to opt out of the service.

A movie based on Zuckerberg and the founding years of Facebook, The Social Network was released on October 1, 2010, and stars Jesse Eisenberg as Zuckerberg. After Zuckerberg was told about the film, he responded, "I just wished that nobody made a movie of me while I was still alive. Also, after the film's script was leaked on the Internet and it was apparent that the film would not portray Zuckerberg in a wholly positive light, he stated that he wanted to establish himself as a "good guy". The film is based on the book The Accidental Billionaires by Ben Mezrich, which the book's publicist once described as "big juicy fun" rather than "reportage". The film's screenwriter Aaron Sorkin told New York magazine, "I don't want my fidelity to be the truth; I want it to be storytelling", adding, "What is the big deal about accuracy purely for accuracy's sake, and can we not have the true be the enemy of the good?"