Cristiano Ronaldo has the most followers on Instagram. Elon Musk claims that title on his platform X (naturally). And Letterboxd has Martin Scorsese.

When he joined in October, shortly after his film “Killers of the Flower Moon” hit theaters, the director quickly became the most-followed account on the burgeoning social media platform, which allows users to rate and review movies, create lists and follow their friends. The director — or whichever canny member of his team is behind the account — doesn’t use the platform as a viewing diary though. Scorsese’s inaugural post was a list of 59 titles cited as companion texts to his own work. In the weeks since, he’s shared a second list of his favorite wide-screen movies.

Scorsese will draw a crowd, but it’s still a bit of an anomaly for an octogenarian to become the most popular account on a social media platform — especially given Letterboxd’s notably younger-skewing audience. Founded in 2011, the platform exploded during the COVID pandemic; it now boasts more than 10 million accounts — five times its size in 2019. But even as those numbers keep climbing, the company says its age demographics haven’t really shifted. Half of the platform’s active users are under 35, and more than half of that group is between 16 and 24.

What’s more, a look at Letterboxd’s annual year-in-review statistics reveals that the portion of current-year releases across all logged films routinely falls below 24%. That means people aren’t just joining the platform to fire off star ratings for “Barbie” or “Five Nights at Freddy’s” — they are more often weighing in on older films.

For the repertory film programming scene in Los Angeles, which was largely shuttered during the pandemic, Letterboxd has proven a boon.

“Within the pandemic grew a real appetite for cinema amongst a certain age bracket, and I think Letterboxd was the way,” says KJ Relth-Miller, director of film programs at the Academy Museum. “I started using Letterboxd during the pandemic — it was one way to connect to folks who didn’t have a community to connect with at their local cinema.”

Likewise, the American Cinematheque, which programs screenings across three L.A. venues, has tripled its membership since before the pandemic.

“With things such as Letterboxd, we’ve seen an uptick in younger people,” says Grant Moninger, the Cinematheque’s artistic director. “If you go to a screening of ‘Rear Window’ or an Akira Kurosawa film, they’ll sell out. And you’d be surprised: The average age for these is probably around 27.”

The platform is even pushing its audience toward the theatrical experience on the level of advertisements on the website, savvily tailored to individual users’ viewing activities.

“We know what people like and what they really like,” Letterboxd editor-in-chief Gemma Gracewood says. “In a marketing sense, we don’t find all the 18-to-24-year-old women in the L.A. area. We’ll find the people in the L.A. area who have rated every previous Todd Haynes movie four stars or more and we’ll advertise screenings for his new film ‘May December.’”

Letterboxd is also cultivating a youth culture in-house. Gracewood made the “crafted editorial decision” to seek out ambitious, developing writers on the site and foster their talent. An early find was Mia Lee Vicino, 27, who now serves as West Coast editor for the website’s online magazine. Vicino counts herself among the Angelenos who prioritize repertory screenings — a habit nurtured by Letterboxd.

“It helped blossom my cinephilia — mostly through thirst-watching Cary Grant’s filmography,” Vicino jokes. “Using Letterboxd helped me gather the courage to move to L.A. and pursue film journalism … It’s genuinely impacted my life. I’m very grateful.”

In between interviewing the likes of Scorsese and Greta Gerwig, Vicino is doing some “casual pitching” to entice other directors to join the platform. Edgar Wright contributed a list of his 100 favorite comedies, while horror favorite Mike Flanagan and “Red Rocket” director Sean Baker maintain prolific profiles. On a recent carpet, Ava DuVernay was eager to share her “Letterboxd four” — referring to the top row on a user’s profile, which showcases a quartet of favorite films. The “Origin” director had started a new, public-facing profile, but she’s not looking for followers on her secret long-time account.

“She went, ‘I’m never going to show people my Letterboxd. It’s too chaotic,’” Gracewood says.

As for Scorsese, whether he’ll stay active on Letterboxd is up to him.

“We asked, ‘Are you going to do your four?’ But he doesn’t play favorites,” Gracewood says. “If all he does is gift us two lists, that’s fine! The guy is busy restoring films and making them.”