Twitter reported a drop in user engagement and projected lower-than-expected revenue, sending its stock price plummeting as much as 12% in after-hours trading.

The social-media company said Monday that timeline views per user dropped 7%, even as total users climbed a healthy 23% to 284 million. And while revenue in the third quarter doubled to $361 million in the third quarter, Twitter’s projected sales of $440 million to 450 million for the next three months fell short of investor expectations, according to Reuters.

The company, which went public last November, said its third-quarter loss grew to $175.5 million from $64.6 million in the same quarter last year.

“I’m confident in our ability to build the largest daily audience in the world, over time, by strengthening the core, reducing barriers to consumption and building new apps and services,” CEO Dick Costolo said in a statement.

Write to Noah Rayman at noah.rayman@time.com.