Back in September 2011, Twitter proudly announced 100 million active users.

Fast-forward six months later to March 2012, and that number had jumped to 140 million. Well, that growth just keeps on coming, as earlier today Twitter announced yet another significant milestone, with the social micro-blogging platform now more than 200 million users strong.

Which means Twitter is continuing to add 40 million new (and, critically, active) users every six months – a little over 1.5 million per week.

The update came via an announcement from the @twitter account a moment after 10am ET, and said: “There are now more than 200M monthly active @twitter users. You are the pulse of the planet. We’re grateful for your ongoing support!”

An active user is defined throughout social media as someone who uses the service at least once per month. Facebook, of course, recently reached it’s one billionth active user, so Twitter has some ways to go before it gets close to Mark Zuckerberg’s behemoth. Still, 2012 was a huge year for Twitter, and this is yet another indication of how big and important it has become to an awful lot of people.