Whisper has closed $21 million to share your secrets. Rather, to let you share your secrets via its mobile apps.

Whisperers add text to images and post it anonymously to the site. You can either upload your own photo or find one within the app. Social features let users see popular, latest, and nearby whispers, and post them to other social networks.

The company was founded in 2012 and is growing fast. It claims to have millions of users and over 2.5 billion page views each month, which is significant for a mobile only startup.

Whispers can include embarrassing moments, intimate confessions, or be a place where people can get things off their chest. Posts range from “Having a friend with benefits isn’t as fun as I thought it would be” to “I am a 20 year old male who plays Pokemon.”

Whisper has also founded a non-profit organization called Your Voice which is dedicated to promoting awareness of mental illness on college campuses. Mental illness and emotional struggles can be stigmatized, and people are often reluctant to share their struggles with people they know. Both Your Voice and Whisper aim to provide a safe place  for expression.

Hallowed venture capital firm Sequoia led this round, with participation from existing investors Lightspeed Venture Partners and Trinity Ventures. Investors, it seems, are bullish about social apps that promote anonymity, privacy, and intimacy.

This is partially due to the popularity of Snapchat, an app that lets you send self-destructing photo messages. Snapchat is now valued at $860 million. The company generates no revenue (yet), so this value is based on its number of users and rate of engagement.  Users are sharing 200 million messages each day.

Whisper and Snapchat are both popular among the teenage-to-early-twenties crowd — users who are smartphone savvy and prone to expressing themselves online. This funding could help Whisper achieve similar success and scale its technology to meet demand.

Whisper is based in Santa Monica, California. This brings its total capital raised to $24 million.  It is available on iOS and Android.