(Spencer Platt/GETTY IMAGES)

Davidsonville resident Clint Stelfox set up two of his friends with each other, but he had no idea he was doing it.

One of those friends — Justin McLeod — recently started a D.C.-based mobile dating app called Hinge, which lets users rank and connect with their friends’ Facebook friends. McLeod, also a Hinge user, used the app to rank Stelfox’s friend, and she’d ranked him. They both independently mentioned their interaction to Stelfox, who isn’t a Hinge user.

“I don’t think there’s any other way they would have met,” Stelfox said.

Depending on each individual’s Facebook privacy settings — if they allow friends of friends to see their friends or their public profile — Hinge connects its users to a pool of their friends’ friends. Though Stelfox is married with a baby and doesn’t use Hinge, his two friends, who were users, found each other because he was their mutual friend on Facebook.

So while he’s not involved in their interaction, Stelfox said he “has a vested interest” in their potential relationship because he’s friends with both of them. “At the very least, I’m going to check up on them,” he said.

Every day at noon, Hinge users — who sign up using their Facebook accounts — receive a batch of 25 profiles of potential matches collected from a pool of their friends’ friends.

Users rank the profiles (which show a name, picture, and any publicly available information from Facebook) on a scale from 1 to 5. If two people rank each other at 4 or 5, Hinge sends a “match” introduction to both.

Hinge founders McLeod and Bennett Richardson designed the app to revolve around mutual friends to provide “social proof” of possible matches. “Having friends in common provides a quick way to confirm whether you should be interested in a person,” Richardson said.

Instead of replacing online dating sites such as OkCupid or eHarmony, McLeod said, Hinge is “more like a helper in your ‘real world’ dating life.” Hinge, which targets users between 18 and 35 years old, is funded by Silicon Valley accelerator 500 Startups and D.C.-based venture fund Fortify.vc, among others.

Hinge’s algorithm weeds out users who are listed on Facebook as married or in a relationship, who aren’t local, and who are out of users’ desired age range.

Building up users

Since its launch last week, Hinge’s app has been installed a couple thousand times, the company said, and has already produced more than 600 matches. The company says it is waiting until the mobile app reaches a critical mass of users to start monetizing it by allowing users to see more information about matches for a monthly subscription fee.

D.C. resident Lauren Wynns, a 30-year-old law student at George Mason University, signed up for the mobile app a few days ago, and checks it about once a day. So far, she has accumulated about a dozen matches.

Wynns ranks users based on their profile picture and quick biographical information — age, location, sometimes where they work or study. When she’s deciding which of her matches to pursue, Wynns immediately looks to their mutual friends for advice.

“I’d shoot [the mutual friend] an e-mail and say, ‘How do you know this person?’” Wynns said, noting that her friend described one of Wynns’s potential matches as a “serial dater,” so Wynns removed him from her list.

Unlike other online dating platforms, “this feels a little more legit because they’re friends of friends, I’m not into complete ‘randoms,’” she said. “I have 1,500 Facebook friends, and people all know that being a ‘Facebook friend’ could mean anything at this point.”