Stories from the set

At the end of the film, we are told that Facebook has 500 million members in 207 countries. At the time of the film's release, the network was used in 196 countries.

Aaron Sorkin's screenplay was based on Ben Mezrich's book «The Accidental Billionaires: The Founding of Facebook, a Tale of Sex, Money, Genius and Betrayal» (2009). Mezrich's book did not claim to accurately recount the circumstances of the creation of the famous social network. Although his works are presented as nonfiction, the dialogues in them are invented, and several real people may correspond to a single character. The author has repeatedly faced accusations of fictionalizing real events, so he prefaced the book about Facebook with a 285-word note stating that the chronology, details, and dialogues do not always correspond to reality.

None of the Facebook employees agreed to take part in the film.

Shia LaBeouf, Michael Cera, and Andrew Garfield were initially considered for the role of Mark Zuckerberg.

In the final frames of the film, a command prompt window is visible on Mark Zuckerberg's laptop, and it can be seen that he was "pinging" localhost, i.e., himself.

The opening scene featuring Jesse Eisenberg and Rooney Mara took up 8 pages of the script, and it took 99 takes to shoot it.

Justin Timberlake lost 15-17 pounds for his role in the film; he believed that a slimmer look would make him appear more youthful.

Director David Fincher tried, but ultimately could not find twin actors for the roles of twins Cameron and Tyler Winklevoss (Zuckerberg's Harvard classmates). So he invited two different actors for each of the brothers – Armie Hammer (Cameron) and Joshua Pence (Tyler). Hammer turned out to be the most similar to the twins. And then Fincher's visual effects team overlaid a CG model of Hammer's face speaking Tyler's lines onto Pence. Thus Hammer played both brothers.

In one of the scenes, it is mentioned that after launching the social network, Mark Zuckerberg became "the most popular person, outdoing nineteen Nobel laureates, fifteen Pulitzer winners, two future Olympians, and a movie star." One of the lawyers clarifies, "Who was the movie star?", and gets the answer — "Does it matter?". That movie star was Natalie Portman, who studied at Harvard from 1999 to 2003.

Justin Timberlake knew Sean Parker even before filming began. Armie Hammer and Joshua Pence met the Winklevoss brothers after the film's premiere. Jesse Eisenberg and Mark Zuckerberg appeared together in one of the SNL episodes (season 36, episode 13).