Police found Swartz's body in his apartment in the New York City borough of Brooklyn on Friday, according to a spokeswoman for the city's chief medical examiner, which ruled the death a suicide by hanging.
Swartz is widely credited with being a co-author of the specifications for the Web feed format RSS 1.0, which he worked on at age 14, according to a blog post on Saturday from his friend, science fiction author Cory Doctorow.
RSS, which stands for Rich Site Summary, is a format for delivering to users content from sites that change constantly, such as news pages and blogs.
Over the years, he became an online icon for helping to make a virtual mountain of information freely available to the public, including an estimated 19 million pages of federal court documents from the PACER case-law system.
"Information is power. But like all power, there are those who want to keep it for themselves," Swartz wrote in an online "manifesto" dated 2008.
"The world's entire scientific and cultural heritage, published over centuries in books and journals, is increasingly being digitized and locked up by a handful of private corporations. ... sharing isn't immoral it's a moral imperative. Only those blinded by greed would refuse to let a friend make a copy," he wrote.
That belief - that information should be shared and available for the good of society - prompted Swartz to found the nonprofit group DemandProgress.
The group led a successful campaign to block a bill introduced in 2011 in the U.S. House of Representatives called the Stop Online Piracy Act.
The bill, which was withdrawn amid public pressure, would have allowed court orders to curb access to certain websites deemed to be engaging in illegal sharing of intellectual property.
Swartz and other activists objected on the grounds it would give the government too many broad powers to censor and squelch legitimate Web communication.
But Swartz faced trouble in July 2011, when he was indicted by a federal grand jury of wire fraud, computer fraud and other charges related to allegedly stealing millions of academic articles and journals from a digital archive at the Massachusetts Institute of Technology.
According to the federal indictment, Swartz - who was a fellow at Harvard University's Edmond J. Safra Center for Ethics - used MIT's computer networks to steal more than 4 million articles from JSTOR, an online archive and journal distribution service.
JSTOR did not press charges against Swartz after the digitized copies of the articles were returned, according to media reports at the time.
Swartz, who pleaded not guilty to all counts, faced 35 years in prison and a $1 million fine if convicted. He was released on bond. His trial was scheduled to start later this year.
'HARSH ARRAY OF CHARGES'
In a statement released Saturday, the family and partner of Swartz praised his "brilliance" and "profound" commitment to social justice, and struck out at what they said were decisions made at MIT and by prosecutors that contributed to his death.
"Aaron's death is not simply a personal tragedy. It is the product of a criminal justice system rife with intimidation and prosecutorial overreach," the statement said.
"The U.S. Attorney's office pursued an exceptionally harsh array of charges, carrying potentially over 30 years in prison, to punish an alleged crime that had no victims," it added.
A spokeswoman for the U.S. Attorney's office said they wanted to respect the family's privacy and did "not feel it is appropriate to comment on the case at this time." MIT could not be reached for comment
Swartz's funeral is scheduled for Tuesday in Highland Park, Illinois. On Saturday, online tributes to Swartz flooded across cyberspace.
"Aaron had an unbeatable combination of political insight, technical skill and intelligence about people and issues," Doctorow, co-editor of the weblog Boing Boing, wrote on the site.
Doctorow wrote that Swartz had "problems with depression for many years."
Swartz also played a role in building the news-sharing website Reddit, but left the company after it was acquired by Wired magazine owner Conde Nast. Recalling that time of his life, Swartz described his struggles with dark feelings.
In an online account of his life and work, Swartz said he became "miserable" after going to work at the San Francisco offices of Wired after Reddit was acquired.
"I took a long Christmas vacation," he wrote. "I got sick. I thought of suicide. I ran from the police. And when I got back on Monday morning, I was asked to resign."
Tim Berners-Lee, who is credited as the most important figure in the creation of the World Wide Web, commemorated Swartz in a Twitter post on Saturday.
"Aaron dead," he wrote. "World wanderers, we have lost a wise elder. Hackers for right, we are one down. Parents all, we have lost a child. Let us weep."
(Reporting by Alex Dobuzinskis in Los Angeles and P.J. Huffstutter in Chicago; Editing by Colleen Jenkins, Doina Chiacu and Philip Barbara)