Twitter’s mixed fourth quarter shows its challenges ahead.

Last year, Twitter executives set ambitious goals for their company, with hopes of attracting more than 100 million new users and doubling revenue by 2023. The last three months of 2021, however, showed the challenges the company must overcome before it can hit its objectives.

Twitter said on Thursday that its revenue grew more slowly than analysts had expected in the last quarter 2021, and the company predicted that it would report a loss in the current quarter. But it added new users, potentially easing concerns that it was having a hard time drawing interest in an increasingly diverse market for social media.

Twitter reported revenue of $1.56 billion in the final three months of 2021, a 22 percent increase from a year earlier but lower than analyst expectations. Twitter said it earned $176 million in income, a 34 percent decline from the year-ago period. The company said it had 217 million daily active users who see ads, a 13 percent increase.

Twitter also announced that its board had authorized a $4 billion buyback of its stock. The company plans to repurchase $2 billion of its shares on what it described as an accelerated timeline, with the remaining $2 billion to be purchased over time. The plan follows an earlier buyback of $2 billion that was authorized in 2020, although $819 million of that program remained unspent.

“It represents confidence in our strategy and execution,” Ned Segal, Twitter’s chief financial officer, said of the share repurchasing plan. “We are putting our money where our mouth is.”

Twitter has said that it plans to grow rapidly over the next two years, reaching 315 million daily active users and $7.5 billion in annual revenue by the end of 2023.

The company added one million daily active users in the United States in the fourth quarter, and five million users internationally. Its total revenue in 2021 was $5.08 billion, a 37 percent increase from the previous year.

Twitter’s stock price swung wildly last week, when Facebook’s parent company, Meta, said that privacy changes introduced by Apple had dampened its advertising business. Investors viewed Meta’s earnings report as a bellwether for the social media industry, but Twitter said that Apple’s privacy changes had a minimal impact on its advertising business.

“Our strong 2021 performance positions us to improve execution and deliver on our 2023 goals,” Parag Agrawal, Twitter’s new chief executive, said in a statement. “We are more focused and better organized to deliver improved personalization and selection for our audience, partners and advertisers.”