Instagram has doubled its user base, to 700 million monthly actives in two years, fueled by Stories, web signups and better onboarding on low-end Android phones. Instagram’s growth rate is actually speeding up. It took just four months to add the last 100 million users since hitting 600 million in December, while it took six months to go from 500 million to 600 million.
For reference, this makes Instagram more than twice the size of Twitter. Soon it might join Facebook’s other properties in the billion-user club, since WhatsApp and Messenger have 1.2 billion users and Facebook 1.8 billion.