Twitter CEO Jack Dorsey AP Images Twitter's stock is crashing, down 10% in after-hours trading, after delivering a revenue forecast that fell well short of Wall Street expectations.

"We're seeing a continuation of the trends discussed last quarter with less overall advertiser demand than expected," Twitter said in its letter to shareholders on Tuesday.

Here are the key numbers:

Q2 revenue: $602 million, up 20% year-over-year, and short of the $607 million expected by analysts.

Q2 EPS (adjusted): $0.13 versus $0.09 expected by analysts.

$0.13 versus $0.09 expected by analysts. Q2 monthly active users: 313 million, up a hair from 310 million in the first quarter of the year.

Q3 revenue guidance: $590 million to $610 million versus $681.4 million expected by analysts.

Twitter's revenue growth continued to slow in the second quarter, expanding 20% year-on-year, compared to the 61% growth it delivered at this time last year. Twitter blamed the slowdown on increasing competition for social-marketing budgets and the fact that the prices it charges to advertise on its service is higher than others.

"This has proven to be a headwind in growing Twitter's share of overall social budgets and in our ability to grow faster in both video and performance advertising," Twitter said.

Meanwhile, the company's number of users continues to be stuck in the mud, with Twitter adding just 3 million new users in the second quarter. In the US, Twitter's monthly active users grew from 65 million to 66 million.

Here's a look at Twitter's stalled user growth:

Twitter

Twitter is trying to rekindle its growth and prove that it can be a mainstream online service to rival Facebook, rather than a niche product. Twitter's monthly active users have stalled over the past year, even as younger rivals such as Snapchat and Instagram are growing rapidly.

Under CEO Jack Dorsey, Twitter is trying to position itself as the go-to destination for live video and updates for following real-time events, from sports to political protests.

But investors are not convinced. Twitter's stock has plunged about 50% from its 52-week high of $36.67, though it's regained some ground in recent weeks after bottoming out under the $14 mark.

Twitter posted a net loss of $107 million, or $0.15 per share, on a GAAP basis in the second quarter.