Twitter has reached the milestone of 500 million registered users.
Twitter statistics web site Twopcharts says the current user base is more than 500,600,000 users. However, Twitter has yet to make any announcement about reaching the milestone.
Twitter was launched in 2006 and still has a little way to go if it is going to catch up with rival Facebook, which has more than 845 million users.
A problem with the figure is that it doesn't represent the number of active users. Twopcharts says, "only Twitter can tell what the exact number is, and how often people log into the system."
It estimates that out of 100,000 new accounts, only 20 to 25 per cent actually go on to become active users. Then only 10 per cent of accounts in active use actually post tweets.
Twopcharts predicts that Twitter will reach the 600 million mark in 103 days on 6 June. At the time of writing 10 new accounts are registered per second.