The site is up to 300,000 users as of this month, and growth has picked up. By our maths, he’s right: At the end of January, Tumblr had 180,000 registered users, and was adding about 17,000 users per month. Since then, it’s grown by two-thirds, adding around 30,000 users a month — roughly doubling its monthly growth rate. Karp still has a way to go to reach his goal of 1 million users by the end of the year, but it’s doable.
What’s next? Revenue. Karp says the Tumblr team is working on 12 “big” pro features — like more customisation options and a link-suggesting tool — which they’ll launch this summer and charge money for.