Instagram has just crossed another milestone, hitting 600 million monthly active users.

For reference, the service hit 500 million monthly active users back in July, along with 300 million daily active users. Instagram hasn’t updated the number of daily active users, so perhaps that number hasn’t crossed a major milestone, but it still shows Instagram has plenty of momentum for a six-year old app. In fact, its growth rate has increased, as it only took the app six months to add 100 million users. It took 9 months to get from 400 million to 500 million.