Could this be the next big social networking site?

Social media's next big thing

If you haven't heard of it yet, you may need to listen in a little more closely as social media site has exploded in the 18 months since its inception, now boasting three billion page views a month.

The site allows users to post 'secrets' or thoughts anonymously, through the use of pictures with bold eye-catching quotes at the top, much like internet 'memes' – which are described as units for carrying cultural symbols or ideas that virally spread across the internet.

The sentiment on Whisper is serious and thought provoking, and the content is often the kind of thing individuals would not want to shout about in public. The look is similar to the long-running PostSecret website, but Whisper has features which make it more of a social network.

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"That moment in the locker room when all your team mates are making fun of gays and you're just sitting there like 'glad you don't know about me'" one reads. Another reads: "I am nervous that our honeymoon will suck since we are both virgins."

Tetra Images - Jessica Peterson | Brand X Pictures | Getty Images

Others are more lighthearted: "I still pick my nose on occasion. Sometimes tissues just don't cut it."

Users tend to use the mobile app for an average of 20 minutes a day, checking content between 8 and 10 times a day, and are aged between 17 and 28, and the majority are female (70 percent), according to Business Insider.

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Jeremy Liew of Lightspeed Venture Partners –the first investor in popular photo messaging application Snapchat, which was reported to have turned down a $3 billion offer from Facebook – told CNBC he was excited about Whisper's incredible growth. Liew invested $3 million in Whisper in April this year.

"Three billion page views a month is a shockingly big number for a company only 18 months old," Liew told CNBC.

Facebook, arguably one of the first hugely successful social networking sites, has reported over one trillion page views per month, by contrast. It has 1.19 billion active users, with 728 million of these active every day.

Co-founder of Whisper Michael Heyward told technology website TechCrunch earlier this year that the site was designed to contrast with the identity focused social networks.

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Where Whisper differs from Facebook, Twitter and Pinterest, however, is that while these sites encourage people to post things they are proud of, like wedding pictures and holiday snaps, Whisper is where users go to spill the secrets they would normally only tell to a close friend. Other users can post supportive comments, and users can respond to one another.

"As is always the case with these companies the most important thing to look at is: are they delighting users? And the bestway to tell is how engaged are they? How often are they using a product? How many times a day are they opening it and how many days per month are they opening it," said Liew.

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"Both with Snapchat and with Whisper we've seen extraordinary engagement," he added.

Users candownload the app for free but have to pay to send messages to other users.

By CNBC's Katie Holliday: Follow her on Twitter @hollidaykatie