Four people, three of whom were roommates—Mark Zuckerberg, Eduardo Saverin, Chris Hughes, and Dustin Moskovitz—founded Facebook in their Harvard University dorm room in February 2004. Originally called thefacebook.com, it was intended as an online directory of all Harvard’s students to help residential students identify members of other residences. In June 2004, Zuckerberg, Hughes and Moskovitz took a year off from Harvard and moved Facebook’s base of operations to Palo Alto, California, and hired eight employees. They were later joined by Sean Parker. At Facebook, Moskovitz was the company’s first chief technology officer and then vice president of engineering; he led the technical staff and oversaw the major architecture of the site, as well as being responsible for the company’s mobile strategy and development.

On October 3, 2008, Moskovitz announced that he was leaving Facebook to form a new company called Asana with Justin Rosenstein, an engineering manager at Facebook. Moskovitz was also the biggest angel investor in the mobile photo-sharing site Path, run by another former member of Facebook, David Morin. It was reported that Moskovitz’s advice was important in persuading Morin to reject a $100 million offer for the company from Google, made in February 2011.

Moskovitz co-founded the philanthropic organization Good Ventures with his girlfriend (and now wife) Cari Tuna in 2011. In June 2012, Good Ventures announced a close partnership with charity evaluator GiveWell. Both organizations “are aiming to do as much good as possible” and thereby align with the goals of effective altruism. Good Ventures has donated approximately $100 million from 2011 onward to GiveWell top charities Against Malaria Foundation, GiveDirectly, Schistosomiasis Control Initiative, and Deworm the World Initiative, as well as standout charities (see Good Ventures for more) and other effective altruist organizations.

For the 2016 United States Presidential election, Moskovitz announced that he and his wife would donate $20 million to support Hillary Clinton, the Democratic Party nominee, arguing that the dangers of a Donald Trump presidency are significant, and that they were making their donation despite being skeptical of allowing large donors to influence election cycles through money. The New York Times quoted Moskovitz’s blog post on the subject: “The Republican Party, and Donald Trump in particular, is running on a zero-sum vision, stressing a false contest between their constituency and the rest of the world.” This made him the third-largest donor in the 2016 campaigns.

The joint collaboration with GiveWell led to a spinoff called the Open Philanthropy Project, whose goal is to figure out the best possible way to use large sums of money (starting with Moskovitz’s multi-billion-dollar fortune) to do the most good. The Open Philanthropy Project has since become a separate organization, and continuously increases its annual giving, having made over $170 million in grants in 2018 alone (see Open Philanthropy Project#Grants made for more).