David Karp, the founder of Tumblr, is leaving. Karp announced his departure in an email to staffers Monday, and a spokesperson for Verizon’s content unit Oath confirmed the departure when contacted by Variety. Karp, who founded Tumblr close to 11 years ago, will officially leave the company by the end of the year.

“My decision comes after months of reflection on my personal ambitions, and at no cost to my hopefulness for Tumblr’s future or the impact I know it can have,” Karp wrote in his email that he also published on his personal Tumblr. “The internet is at a crossroads of which this team can play a fundamental role in shaping. You are in the driver seat, and I am so excited to see where you go!”

“David founded Tumblr ten years ago as a space for the world’s creators, and we thank him for his commitment and passion driving the growth of the platform to almost 380 million blogs and over 155 billion posts,” an Oath spokesperson said via email. “Going forward, Jeff D’Onofrio, President and COO of Tumblr, will continue to lead the team.”

Karp launched Tumblr in February of 2007 as a blogging service with a built-in social layer that allows users to easily annotate and repost other users’ posts. Yahoo acquired Tumblr for $1.1 billion in 2013, but struggled to monetize the service in a way that would have warranted the price tag. Tumblr ultimately became part of Verizon’s Oath subsidiary through the telco’s $4.5 billion Yahoo acquisition this year.