Facebook's Instagram has passed 400 million monthly active users, as its popularity keeps increasing mainly in countries outside the U.S. That compares with Twitter’s 316 million and Pinterest’s 100 million. Instagram’s number increased from the 300 million mark reached nine months ago, according to the company. Facebook has 1.49 billion monthly active users.

More than 75 percent of Instagram’s users live outside the U.S., with most of the new participants coming from Brazil, Japan and Indonesia, the company said.

The photo-sharing application has started to ramp up its advertising business, taking advantage of Facebook’s network of tools and marketers to increase its offerings and global reach. By the end of the yrear, Instagram will be advertised in more than 200, the company has said.