Pinterest is raising $500 million at an $11 billion valuation, according to The Wall Street Journal.

The round would value the social image-sharing network at more than double what it was worth last May, when it raised $200 million at a $5 billion valuation.

Pinterest is like a digital bulletin board with a social twist. Users can take pictures from anywhere and "pin" them to a board, then follow users and boards that are on particular topics.

Last week, Pinterest raised the ire of some long-time users when it got rid of the ability to make money through affiliate links. That feature allowed users to pin images of favorite products along with links to stores where people could buy them. They got a cut of every transaction.

Pinterest is reportedly adding a "Buy" button, which would mean it is getting more directly into e-commerce itself.

The company also added the ability to download iOS apps directly from pinned images rather than forcing users to go through the Apple App Store. This could help app makers with discovery and also give users a more convenient way of discovering and getting new apps — they can simply download them based on the recommendations of friends on Pinterest.

This week has been a particularly hot time for tech startups to raise money. Also Wednesday, reports emerged that Uber's latest round was oversubscribed and that the ride-hailing company would expand the round by $1 billion to a total of $2.8 billion — the company is valued at over $40 billion. The mobile-messaging company Snapchat is raising a round at $16 billion to $19 billion, almost twice what it was worth last year. The fantasy-sports startup FanDuel is raising a round that would place it in the billion-dollar club.

And overall, the number of billion-dollar privately held mobile tech startups ("unicorns") has doubled in the past year.