Twenty-seven-year-old Justin Mateen knows a whole lot about your dating life. He knows how old you are, how many Facebook friends you have and what physical characteristics you're most attracted to in a potential mate — that is, if you're a member of the nationwide, L.A.-made dating app, Tinder, which uses GPS to locate potential matches nearby.

The iPhone app's addictive, game-like premise is that users anonymously reject others almost solely based on their profile pictures. They can also initiate conversation with only those they're actually interested in, under the condition that the interest is mutual. There are no personal statements, compatibility quizzes or rating systems.

Since launching Tinder in September 2012 with CEO and fellow USC alum Sean Rad, Mateen says the app has made more than 40 million matches — or, two people who mutually click the “heart” button on each other's profiles — plus eight marriage proposals and counting. Not bad for a free app that was locally developed less than a year ago.

Currently only available for the iPhone, the app pulls photos and information from your Facebook profile to let others know if you share mutual friends or common interests. Not feeling any of the profiles that appear in your feed? Just “x” them out to prevent any communication with that user. When you find the profiles you like, click the green “heart” icon below their profile to enable messaging. If they click the same icon on your own profile, then you've got a match. Commence messaging. And if you're feeling daring, break away from Tinder's interface and ask for their phone number. Perhaps you'll even meet in person.

“Tinder emulates the way the real world works,” CMO Mateen tells L.A. Weekly over the phone. “We use it to increase interaction. Right now when you go on Tinder, it's as if you're at a bar or a coffee shop, but instead, you can meet all of those people.”

When I tried out the app, I found that my most common shared interest with other users was that we had all liked L.A. Weekly on Facebook. I struck up text conversations with people who went to high school with my college professors in the Midwest, or were Facebook friends with people I had traveled with in the Middle East. Tinder's concept might be shallow, but its ability to connect us with people we actually want to know can be pretty incredible.

“When you first meet someone, the first thing you notice about them is their physical appearance,” Mateen says. “But once you start talking to them, you look for mutual friends and mutual interests. The reason we [connect the app to] Facebook is because [it contains] authentic data.”

That sense of transparency is part of the reason I agreed to meet two different Tinder users in person. Neither progressed much farther than one date, but if nothing else, it was a good excuse to check out a new bar and talk music, TV and work with an almost-total-stranger whose company was actually kind of enjoyable. In fact, it was surprisingly not awkward at all. That is, up until one of those Tinder users blocked me on the app, allegedly because I turned down his invitation to “check out his apartment down the street” later that same evening. Now we know why Tinder is referred to by critics as a “hook-up app.”

Whether its nickname always rings true or not, there's a science to the matchmaking. Clicking on those “x” and “heart” icons affects more than just your relationship with that one person — it also skews Tinder's algorithm, which is constantly being tweaked. If you “heart” users within a similar age range and that share physical characteristics and a mutual friend or two, Tinder will show you more profiles that fit your perceived preferences. Meanwhile, it will attempt to filter out the type of users that you're rejecting.

“We look at your whole social graph,” Mateen tells us. “We see that you have a certain amount of friends. We're not going to try to pair you up with someone that only has 100 friends.” They also look at how you interact on Tinder. “The same way Pandora kind of figures out your taste in music, we're trying to figure out how you want to meet people.”

Operating out of a West Hollywood office whose previous and current tenants include Ticketmaster and tech start-up Evite, respectively, Tinder's four co-founders are all in their mid-to-late 20s and collectively hold bachelor's degrees in business and marketing. But Tinder, their most popular tech venture, is far from their first.

Tinder screenshots

Tinder screenshots

Before Tinder ignited the flames of mobile romance and the funding from IAC, the New York-based Internet giants behind and OKcupid, Mateen founded Sitecanvas, a website builder that he says was used to create and maintain sites for Taylor Swift, supermodel Adriana Lima and other celebrities. Meanwhile, Rad founded a matchmaking service of his own: Adly, a startup that matches celebrities seeking to endorse products on Twitter with companies willing to pay for those endorsements.

The idea for Tinder was sparked when Mateen “noticed on Instagram and on Facebook that people were exchanging their phone numbers on photos, trying to meet new people. So we cut the fat and just made it a direct, honest way to meet.” Up until Tinder, whose name refers to lighting a fire, Mateen felt that “most social platforms do a wonderful job of cultivating existing relationships, but there hasn't been a successful way to meet new people [through social media].”

It's hard to judge Tinder's success rate when it comes to matching compatible couples, short-term hookups or even platonic “friends,” as Mateen suggests, but it helps that users — 70 percent of which are between the ages of 18-24 — aren't embarrassed to use the app in public. “It's crazy that people are resorting to Tinder in social situations,” he says.

He's seen it firsthand. While at a party at Trump Hotel in New York, Mateen observed a group of models glued to the couch all night, obsessively flipping through profiles on Tinder. It didn't take him long to strike up a conversation with one of the girls after realizing that they had been Tinder-matched just the night before.

The co-founders plan to use their addictive algorithm to extend the app's matchmaking services — no matter how superficial — beyond the realm of dating. “Dating was a starting point for us. [In the future] people will be using it for friendships, for business relationships, and to some extent, people already are.”

But do you really want to find your next business partner based almost solely on their good looks and youthfulness? Maybe not. But pretty soon, Tinder will be an app for that, too.

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