Aaron Swartz, who helped develop the Web feed format RSS and co-founded Reddit before killing himself last year at age 26, is the subject of “The Internet’s Own Boy.” (NOAH BERGER/REUTERS)

It’s impossible to imagine how different the world would be if Aaron Swartz hadn’t killed himself in early 2013, because the computer whiz was the kind of visionary who saw a future others couldn’t fathom. When he was developing the technology to make RSS feeds a reality, his brother probably wasn’t the only one to ask, “Why is that useful?” Some people just have keener foresight.

Barely a year after Swartz’s death, documentarian Brian Knappenberger debuted “The Internet’s Own Boy: The Story of Aaron Swartz” at the Sundance Film Festival. That’s quite a turnaround for a movie about the prodigy’s life and death, especially one this rousing and persuasive.

Even posthumously, no one is claiming Swartz was perfect. Family members and girlfriends describe him as difficult. He had a strong personality and sometimes rubbed people the wrong way. When he shifted into explainer mode, he could come across as a twerp. But his genius was undeniable. He picked up new concepts easily and the documentary includes home movies of Swartz reading at 3 years old.

As he grew up, his attention turned to computers. In addition to the RSS format, he also dreamed up a user-generated encyclopedia that predated Wikipedia and co-founded the Web site Reddit. One of Swartz’s friends describes that sprawling social-media-meets-news site as bordering on chaos, and Swartz probably relished that aspect of it. He was never big on school, dropping out of Stanford because he felt like he was being babysat, and he couldn’t fathom a 9-to-5 grind. Condé Nast, which acquired Reddit, fired Swartz, reportedly because he never showed up for work.

This need for freedom got Swartz into trouble with the law. When he was caught sneaking onto the campus of MIT to download academic articles from the university’s servers, federal prosecutors were set on making an example of him. He was charged with 13 felony counts, which carried a potential penalty of 35 years in prison and $1 million in fines. After a two-year legal battle that sapped his spirit and drained his bank account, the 26-year-old hanged himself.

Knappenberger’s documentary is smart and focused, homing in on a recurring theme of independence. Swartz was an open-access proponent who couldn’t even handle the supervision of university life. But prosecutors sought at least some jail time (one plea deal offered three months behind bars, time at a halfway house and house arrest — all without the use of a computer). It’s hard to imagine Swartz, with his drive for freedom, serving time.

The movie does no favors for prosecutor Stephen Heymann, who declined to be interviewed and is painted as a villain with an ax to grind. The director also just barely touches on a larger issue, which is that Swartz is hardly the only person who has been targeted by authorities for a minor offense. The difference is that Swartz is white.

But even as a microcosm of a broader problem, Swartz’s story remains heartbreaking, especially as we see his family and friends recount how they learned the news of Swartz’s death. They lost a loved one, and their still-fresh sadness is difficult to watch, but the rest of the world lost something, too: an exciting mind, capable of making real changes that may never come to pass.

★ ★ ★

Unrated. At West End Cinema. Contains strong language. 105 minutes.