Twitter chief operating officer Dick Costolo revealed that the company is seeing 190 million unique visitors a month and 65 million tweets a day in New York today.

The choice of metrics is interesting, in part, because Twitter is using one of the highest possible numbers afforded to it. The microblogging service, which lets users post tweets, or short, 140-character updates visible to everyone on the Internet or just friends, is counting all visitors, not active users or even registered users. By the same metrics, Facebook could claim to have 1.2 billion unique visitors a month. (Facebook publicly says it has more than 400 million active users, but that figure may be closer to 500 million now, since it’s four months old and Facebook continues to grow quickly.)

Of course, from another perspective, Twitter’s figures could also underestimate usage somewhat. There are plenty of users who access Twitter completely independently of the website. The microblogging network said 75 percent of its traffic came via its application programming interfaces during its April developer conference in San Francisco. At the same event, the company said it had 105 million registered users. It added that it was seeing 300,000 new users a day. If its growth stayed consistent,  then the service would have about 122 million registered users by now.