Just over nine years since the launch of its file hosting service Dropbox has announced it has reached the milestone of 500 million users.

According to the company, Dropbox users have created 3.3 billion connections by sharing with each other. To date, the company’s marketing policy seems to revolve around word-of-mouth, as 44% of new accounts were opened when existing users introduced people to the service.

Founded in 2007 by MIT students Drew Houston and Arash Ferdowsi, the early idea arose after Houston repeatedly forgot his USB flash drive. Initially a personal tool for Houston, the potential was soon realized and shortly thereafter seed funding was provided from startup fund Y Combinator.

After initially focusing on the consumer market, Dropbox officially ventured into the B2B space during 2011 and has continued to grow in recent years. Having evolved into Dropbox for Business and then adding Dropbox for Enterprise last year, the service is now used is more than 8 million businesses, with 150,000 using the premium service. Strong growth is expected to continue as 25,000 corporate customers bolster the ranks each quarter.

Dropbox still boasts a strong US following, though recent growth has come from worldwide markets. The team highlighted that 75% of users are based outside the US, with the majority of the last 100 million coming from Germany, US, India, Brazil and the UK.

While Dropbox has received substantial international growth, the brand still experiences resistance from Chinese authorities. The service was banned in the country from May 2010, with most in the community considering the censorship evidence of Dropbox’s growing international popularity and influence. The service was unblocked between February and June 2014, before being reinstated on the censored list. Today, it still remains unclear as to why Dropbox was uncensored for this period.

While user growth has continued, Dropbox has come under scrutiny in recent months following rival Box’s January 2015 IPO, which valued the company significantly lower than expected. The news has put pressure on Dropbox, whose last funding round valued it at $10 billion, though many believe the current value to be substantially lower.

Executives at Dropbox have rigorously defended its position, market capabilities and future outlook, highlighting user growth as a demonstration of market demand. Dennis Woodside recently commented to Forbes “We are continuing the scaling of the business across both consumer and enterprise.”