Twitter Inc. (TWTR) posted stronger-than-expected fourth quarter earnings Thursday as the micro-blogging website held user growth but said expenses would rise notably this year as it moved to protect the integrity of its platform.

Twitter said earnings for the three months ending in December came in a 31 cents per share, rising 63% from last year and topping the Street forecast of 25 cents per share. Group revenues, Twitter said, rose 24 to $909 million and again topped the consensus forecast of $868 million.

Looking into 2019, Twitter said it see first quarter revenue in the region of $715 to $775 million, essentially in-line with the Refinitiv forecast of $765 million. Twitter also said GAAP and cash operating expenses would rise by 20% from last year, to a range of $550 million to $600 million, "as we support our existing priorities of health, conversation, revenue product and sales, and platform."

"2018 is proof that our long-term strategy is working. Our efforts to improve health have delivered important results, and new product features like a single switch to move between latest and most relevant Tweets have been embraced by the people who use Twitter," said CEO Jack Dorsey. "We enter this year confident that we will continue to deliver strong performance by focusing on making Twitter a healthier and more conversational service."

Twitter shares closed down 9.84% to $30.80 Thursday.

Twitter said the average of daily active users that the company can monetize on its platform rose 9% to 126 million, helped by an 11% gain in international users to 99 million. On a monthly basis, Twitter said, active users were down 9 million to 321 million, but that figure came in largely in-line with analysts' forecasts. 

However, Twitter also said it would stop publishing monthly active user data after the first quarter of this year, and would immediately start providing daily active user data for U.S. and international markets.