Business Insider/Alyson Shontell

Michael Heyward, CEO of Whisper, in the Santa Monica office. The office is house with a pool, a giant trampoline, a basketball court and a gas fireplace (pictured).

If you open mobile app Whisper, it looks like a collection of Internet memes. Each entry is a picture with bold text on top, created in seconds by users.Unlike memes, Whisper’s photo messages aren’t often funny.

They’re thought-provoking and serious; the kind of secrets only best friends reveal to each other.

“That moment in the locker room when all your teammates are making fun of gays and you’re just sitting there like ‘glad you don’t know about me…'” one popular Whisper reads.

Whisper

A post on Whisper.

There are some light-hearted messages on Whisper too.

“Snow, the only time a girl gets excited over three inches,” is one example.

Reading Whisper is like “watching a trainwreck,” one user told Business Insider. It’s hard to pull your eyes away.

The two-year-old app is rapidly gaining popularity. Millions of people use Whisper and it is approaching 3 billion monthly pageviews. On average, people spend more than 20 minutes per day with Whisper, checking its content 8–10 times per day. Whisper has raised $25 million from early Snapchat investor Lightspeed and others.

The people who are spilling their guts on Whisper fall between ages 17 and 28. Heyward says fewer than 4% of his users are under the age of 18. The vast majority of its users — 70% — are women.

The reason Whisper gets so many people to share things they’d never say out loud is because everything is posted anonymously. In the past, anonymous social networks have been nasty places. Just look at the comments on YouTube, or at failed startups like Juicy Campus, which were sued by people defamed on their sites.

Michael Heyward, the app’s 26-year-old founder, has gone to great lengths to keep Whisper’s content respectful. He never wants anyone to read Whisper and feel like they need to shower. He has 92 people moderating content and comments in the Philippines in addition to the 32 people Whisper employs full-time.

Business Insider/Alyson Shontell

The Whisper house sits in a residential neighborhood in Santa Monica, where 32 people work, occasionally sleep, and hack away at the app.

“You are who you are when no one else is looking,” Heyward told Business Insider at his Santa Monica headquarters in early December. “Anonymity is a really powerful tool. But we think about it like that Spiderman’ quote: ‘With great power comes great responsibility.’ Think about all the things you can do with a hammer. You can build something great … or you can kill someone.”

Heyward occasionally teaches at USC. In a recent class, he asked students to raise their hands if they were virgins. No one did. Then he blindfolded them, turned off the lights, and asked the same question. Half of the hands went up. Think of the first scenario as Facebook and the second as Whisper.

Facebook, Pinterest and Twitter are social networks tied to identities. Because of that, people only share things they’re proud of, like engagements, articles, weddings, vacations and pregnancies. Heyward, who grew up in Los Angeles and went to the same high school as Snapchat CEO Evan Spiegel, says he’s innovating loneliness.

Anonymity is a really powerful tool. Think about all the things you can do with a hammer. You can build something great, or you can kill someone.

Heyward’s mission is to make sure people only use anonymity on Whisper to protect themselves and not to hurt someone else. The result is something that looks like an open-source diary, with supportive comments from people who understand the intense feelings being described.  Often, users will respond to one Whisper with another.

Not all of Whisper’s content is real. A few posts are dreamt up by imaginative users. But for the many that are, Whisper acts like a therapy group that connects people based on intimate, shared experiences. Some Whisper users say the app has saved their lives.