Instagram has hit a new milestone: 400 million monthly active users. The stat was announced in a blog post this afternoon, just about 10 months after Instagram first hit 300 million monthly active users. Instagram's growth from 200 million to 300 million happened in roughly the same timespan, which means that the service is growing fast, although its growth is not necessarily accelerating. Still, it's grown to an impressive size. Twitter is currently at 316 million monthly active users, and Pinterest just hit 100 million.
What's particularly interesting about Instagram's growth is that it's happening largely outside of the US. Instagram says that 75 percent of its users live elsewhere, with recent growth coming from Europe and Asia; Brazil, Japan, and Indonesia added the most users in this past 100 million. In total, Instagram says that its users are posting 80 million photos per day.