Twitter Inc. (TWTR - Get Report) posted stronger-than-expected third earnings Thursday but said monthly active users fell a bit more than anticipated, suggesting moves by the micro-blogging website to limit hate speech and cull fake accounts are having an impact.

Twitter said adjusted earnings the three months ending in September jumped to 21 cents a share, well head of the Street's forecast of 14 cents a share. Group revenues, Twitter said, rose 29% to $758 million, again topping the consensus estimate of $704 million. Monthly active users, however, fell 4 million to 326 million, missing analysts' forecasts, and it saw a 20% quarter-on-quarter decline in new sign-ups since it introduced new techniques for detecting potential malicious accounts.

"We're achieving meaningful progress in our efforts to make Twitter a healthier and valuable everyday service," said CEO Jack Dorsey. "We're doing a better job detecting and removing spammy and suspicious accounts at sign-up. We're also continuing to introduce improvements that make it easier for people to follow events, topics and interests on Twitter, like adding support for U.S. TV shows in our new event infrastructure."

"This quarter's strong results prove we can prioritize the long-term health of Twitter while growing the number of people who participate in public conversation," he added.

Twitter shares were marked 20% higher in the opening 30 minutes of trading Thursday and changing hands at $33.00 each, a move that takes the stock's year-to-date advance past 37% and values the San Francisco, Calif.-based group at more than $25 billion. 

Twitter said ad revenues, its most important driver, rose 29% to $650 million, thanks in part to moves to live-stream professional sports events such as Major League Baseball and Major League Soccer.