Twitter CEO Dick Costolo revealed today that the service currently has 100 million "active" users, and receives around 400 million pageviews per month.

During a "state of the union” meeting this morning at Twitter’s San Francisco headquarters, CEO Dick Costolo revealed, for the first time ever, that the service currently has 100 million active users, and receives 400 million pageviews per month, up from about 250 million in January of this year.

In addition, Costolo said that half of Twitter’s users log on ever day, but only 60 percent actually publish tweets. The remainder simply read others’ tweets. Some never even login, even if they have an account.

"The 400 million monthly uniques number shows that people are getting value out of Twitter without logging in,” said Costolo.

Costolo said that the company is working to turn passive Twitter users into active ones, as much as possible.

Approximately 55 percent of Twitter users log on through a mobile device, which is about 40 percent up from the previous quarter, Costolo said. And the number of tweets published is averaging about 1 billion per week.